Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $41.41   8.200%   $44.8056   $44.81   $44.80   $44.80  
  Purchase #2 $174.87   10.347%   $192.9638   $192.96   $192.95   $193.00  
  Purchase #3 $198.90   6.123%   $211.0786   $211.08   $211.10   $211.10  
  Purchase #4 $221.81   6.131%   $235.4092   $235.41   $235.40   $235.40  
  Purchase #5 $180.40   13.717%   $205.1455   $205.15   $205.15   $205.10  
  Purchase #6 $195.28   4.285%   $203.6477   $203.65   $203.65   $203.60  
  Purchase #7 $172.94   11.770%   $193.295   $193.30   $193.30   $193.30  
  7 purchase totals = $1,185.61       $1,286.3454   $1,286.36   $1,286.35   $1,286.30