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	$178.62	8.701%	$194.1617	$194.16	$194.15	$194.20
Purchase #2	$222.43	12.588%	$250.4295	$250.43	$250.45	$250.40
Purchase #3	$81.77	4.287%	$85.2755	$85.28	$85.30	$85.30
Purchase #4	$212.32	4.609%	$222.1058	$222.11	$222.10	$222.10
Purchase #5	$119.89	7.540%	$128.9297	$128.93	$128.95	$128.90
Purchase #6	$150.29	10.224%	$165.6556	$165.66	$165.65	$165.70
Purchase #7	$129.25	10.431%	$142.7321	$142.73	$142.75	$142.70
7 purchase totals =	$1,094.57		$1,189.2899	$1,189.30	$1,189.35	$1,189.30