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	$184.49	7.756%	$198.799	$198.80	$198.80	$198.80
Purchase #2	$37.43	10.309%	$41.2887	$41.29	$41.30	$41.30
Purchase #3	$239.66	6.679%	$255.6669	$255.67	$255.65	$255.70
Purchase #4	$65.32	10.663%	$72.2851	$72.29	$72.30	$72.30
Purchase #5	$56.45	6.227%	$59.9651	$59.97	$59.95	$60.00
Purchase #6	$194.61	4.123%	$202.6338	$202.63	$202.65	$202.60
Purchase #7	$231.76	9.414%	$253.5779	$253.58	$253.60	$253.60
7 purchase totals =	$1,009.72		$1,084.2165	$1,084.23	$1,084.25	$1,084.30