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	$126.91	11.325%	$141.2826	$141.28	$141.30	$141.30
Purchase #2	$237.25	7.235%	$254.415	$254.42	$254.40	$254.40
Purchase #3	$225.76	13.565%	$256.3843	$256.38	$256.40	$256.40
Purchase #4	$93.46	12.486%	$105.1294	$105.13	$105.15	$105.10
Purchase #5	$108.40	9.347%	$118.5321	$118.53	$118.55	$118.50
Purchase #6	$59.79	3.506%	$61.8862	$61.89	$61.90	$61.90
Purchase #7	$194.94	13.800%	$221.8417	$221.84	$221.85	$221.80
7 purchase totals =	$1,046.51		$1,159.4713	$1,159.47	$1,159.55	$1,159.40