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	$92.48	7.622%	$99.5288	$99.53	$99.55	$99.50
Purchase #2	$227.72	7.284%	$244.3071	$244.31	$244.30	$244.30
Purchase #3	$57.82	5.718%	$61.1261	$61.13	$61.15	$61.10
Purchase #4	$85.48	11.418%	$95.2401	$95.24	$95.25	$95.20
Purchase #5	$120.32	3.681%	$124.749	$124.75	$124.75	$124.70
Purchase #6	$51.55	13.434%	$58.4752	$58.48	$58.50	$58.50
Purchase #7	$90.58	10.640%	$100.2177	$100.22	$100.20	$100.20
7 purchase totals =	$725.95		$783.6440	$783.66	$783.70	$783.50