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	$130.72	4.667%	$136.8207	$136.82	$136.80	$136.80
Purchase #2	$161.83	7.800%	$174.4527	$174.45	$174.45	$174.50
Purchase #3	$52.62	13.446%	$59.6953	$59.70	$59.70	$59.70
Purchase #4	$71.89	6.503%	$76.565	$76.57	$76.55	$76.60
Purchase #5	$139.67	13.271%	$158.2056	$158.21	$158.20	$158.20
Purchase #6	$80.71	13.390%	$91.5171	$91.52	$91.50	$91.50
Purchase #7	$228.67	10.281%	$252.1796	$252.18	$252.20	$252.20
7 purchase totals =	$866.11		$949.4360	$949.45	$949.40	$949.50