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	$188.83	9.132%	$206.074	$206.07	$206.05	$206.10
Purchase #2	$182.87	6.778%	$195.2649	$195.26	$195.25	$195.30
Purchase #3	$227.85	13.549%	$258.7214	$258.72	$258.70	$258.70
Purchase #4	$52.34	3.743%	$54.2991	$54.30	$54.30	$54.30
Purchase #5	$244.67	12.627%	$275.5645	$275.56	$275.55	$275.60
Purchase #6	$74.80	10.635%	$82.755	$82.76	$82.75	$82.80
Purchase #7	$7.35	7.556%	$7.9054	$7.91	$7.90	$7.90
7 purchase totals =	$978.71		$1,080.5843	$1,080.58	$1,080.50	$1,080.70