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	$163.53	9.629%	$179.2763	$179.28	$179.30	$179.30
Purchase #2	$159.89	13.730%	$181.8429	$181.84	$181.85	$181.80
Purchase #3	$155.68	9.799%	$170.9351	$170.94	$170.95	$170.90
Purchase #4	$59.92	13.132%	$67.7887	$67.79	$67.80	$67.80
Purchase #5	$57.67	3.428%	$59.6469	$59.65	$59.65	$59.60
Purchase #6	$139.81	8.138%	$151.1877	$151.19	$151.20	$151.20
Purchase #7	$191.45	4.324%	$199.7283	$199.73	$199.75	$199.70
7 purchase totals =	$927.95		$1,010.4059	$1,010.42	$1,010.50	$1,010.30