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	$116.80	5.753%	$123.5195	$123.52	$123.50	$123.50
Purchase #2	$98.32	12.799%	$110.904	$110.90	$110.90	$110.90
Purchase #3	$42.80	13.414%	$48.5412	$48.54	$48.55	$48.50
Purchase #4	$47.79	13.464%	$54.2244	$54.22	$54.20	$54.20
Purchase #5	$39.48	8.539%	$42.8512	$42.85	$42.85	$42.90
Purchase #6	$236.97	5.694%	$250.4631	$250.46	$250.45	$250.50
Purchase #7	$144.99	6.747%	$154.7725	$154.77	$154.75	$154.80
7 purchase totals =	$727.15		$785.2759	$785.26	$785.20	$785.30