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	$164.46	6.717%	$175.5068	$175.51	$175.50	$175.50
Purchase #2	$183.97	10.396%	$203.0955	$203.10	$203.10	$203.10
Purchase #3	$38.62	5.690%	$40.8175	$40.82	$40.80	$40.80
Purchase #4	$186.57	12.698%	$210.2607	$210.26	$210.25	$210.30
Purchase #5	$151.94	11.217%	$168.9831	$168.98	$169.00	$169.00
Purchase #6	$100.54	3.460%	$104.0187	$104.02	$104.00	$104.00
Purchase #7	$109.59	4.238%	$114.2344	$114.23	$114.25	$114.20
7 purchase totals =	$935.69		$1,016.9167	$1,016.92	$1,016.90	$1,016.90