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	$50.29	3.682%	$52.1417	$52.14	$52.15	$52.10
Purchase #2	$192.89	11.702%	$215.462	$215.46	$215.45	$215.50
Purchase #3	$64.82	10.528%	$71.6442	$71.64	$71.65	$71.60
Purchase #4	$78.37	11.512%	$87.392	$87.39	$87.40	$87.40
Purchase #5	$121.88	7.816%	$131.4061	$131.41	$131.40	$131.40
Purchase #6	$150.93	5.722%	$159.5662	$159.57	$159.55	$159.60
Purchase #7	$185.36	6.766%	$197.9015	$197.90	$197.90	$197.90
7 purchase totals =	$844.54		$915.5137	$915.51	$915.50	$915.50