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	$222.85	9.852%	$244.8052	$244.81	$244.80	$244.80
Purchase #2	$244.91	8.500%	$265.7274	$265.73	$265.75	$265.70
Purchase #3	$57.29	7.285%	$61.4636	$61.46	$61.45	$61.50
Purchase #4	$168.93	13.576%	$191.8639	$191.86	$191.85	$191.90
Purchase #5	$65.89	6.683%	$70.2934	$70.29	$70.30	$70.30
Purchase #6	$50.69	4.259%	$52.8489	$52.85	$52.85	$52.80
Purchase #7	$195.87	4.283%	$204.2591	$204.26	$204.25	$204.30
7 purchase totals =	$1,006.43		$1,091.2615	$1,091.26	$1,091.25	$1,091.30