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 $32.69   6.558%   $34.8338   $34.83   $34.85   $34.80  
  Purchase #2 $33.52   4.339%   $34.9744   $34.97   $34.95   $35.00  
  Purchase #3 $153.86   12.337%   $172.8417   $172.84   $172.85   $172.80  
  Purchase #4 $204.28   4.415%   $213.299   $213.30   $213.30   $213.30  
  Purchase #5 $186.54   6.346%   $198.3778   $198.38   $198.40   $198.40  
  Purchase #6 $223.29   9.276%   $244.0024   $244.00   $244.00   $244.00  
  Purchase #7 $140.95   4.702%   $147.5775   $147.58   $147.60   $147.60  
  7 purchase totals = $975.13       $1,045.9066   $1,045.90   $1,045.95   $1,045.90