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	$123.34	7.768%	$132.9211	$132.92	$132.90	$132.90
Purchase #2	$243.63	13.591%	$276.7418	$276.74	$276.75	$276.70
Purchase #3	$125.73	5.352%	$132.4591	$132.46	$132.45	$132.50
Purchase #4	$227.47	9.831%	$249.8326	$249.83	$249.85	$249.80
Purchase #5	$57.50	13.691%	$65.3723	$65.37	$65.35	$65.40
Purchase #6	$185.34	5.859%	$196.1991	$196.20	$196.20	$196.20
Purchase #7	$107.51	6.631%	$114.639	$114.64	$114.65	$114.60
7 purchase totals =	$1,070.52		$1,168.1650	$1,168.16	$1,168.15	$1,168.10