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	$205.51	3.128%	$211.9384	$211.94	$211.95	$211.90
Purchase #2	$140.42	11.281%	$156.2608	$156.26	$156.25	$156.30
Purchase #3	$94.46	11.261%	$105.0971	$105.10	$105.10	$105.10
Purchase #4	$109.67	11.368%	$122.1373	$122.14	$122.15	$122.10
Purchase #5	$74.68	12.341%	$83.8963	$83.90	$83.90	$83.90
Purchase #6	$20.38	6.413%	$21.687	$21.69	$21.70	$21.70
Purchase #7	$206.57	13.508%	$234.4735	$234.47	$234.45	$234.50
7 purchase totals =	$851.69		$935.4904	$935.50	$935.50	$935.50