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	$221.81	4.290%	$231.3256	$231.33	$231.35	$231.30
Purchase #2	$59.63	12.165%	$66.884	$66.88	$66.90	$66.90
Purchase #3	$44.30	13.102%	$50.1042	$50.10	$50.10	$50.10
Purchase #4	$68.61	6.164%	$72.8391	$72.84	$72.85	$72.80
Purchase #5	$177.99	12.241%	$199.7778	$199.78	$199.80	$199.80
Purchase #6	$97.78	13.853%	$111.3255	$111.33	$111.35	$111.30
Purchase #7	$86.91	8.449%	$94.253	$94.25	$94.25	$94.30
7 purchase totals =	$757.03		$826.5092	$826.51	$826.60	$826.50