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	$212.32	11.214%	$236.1296	$236.13	$236.15	$236.10
Purchase #2	$71.91	5.785%	$76.07	$76.07	$76.05	$76.10
Purchase #3	$71.36	8.731%	$77.5904	$77.59	$77.60	$77.60
Purchase #4	$109.61	12.358%	$123.1556	$123.16	$123.15	$123.20
Purchase #5	$79.51	12.738%	$89.638	$89.64	$89.65	$89.60
Purchase #6	$183.54	11.770%	$205.1427	$205.14	$205.15	$205.10
Purchase #7	$217.37	3.193%	$224.3106	$224.31	$224.30	$224.30
7 purchase totals =	$945.62		$1,032.0369	$1,032.04	$1,032.05	$1,032.00