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	$199.70	10.835%	$221.3375	$221.34	$221.35	$221.30
Purchase #2	$89.31	4.287%	$93.1387	$93.14	$93.15	$93.10
Purchase #3	$172.66	4.302%	$180.0878	$180.09	$180.10	$180.10
Purchase #4	$105.76	5.365%	$111.434	$111.43	$111.45	$111.40
Purchase #5	$123.72	5.768%	$130.8562	$130.86	$130.85	$130.90
Purchase #6	$232.51	3.426%	$240.4758	$240.48	$240.50	$240.50
Purchase #7	$51.62	13.672%	$58.6775	$58.68	$58.70	$58.70
7 purchase totals =	$975.28		$1,036.0075	$1,036.02	$1,036.10	$1,036.00