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	$55.38	11.566%	$61.7853	$61.79	$61.80	$61.80
Purchase #2	$151.60	11.819%	$169.5176	$169.52	$169.50	$169.50
Purchase #3	$64.68	12.230%	$72.5904	$72.59	$72.60	$72.60
Purchase #4	$89.46	10.216%	$98.5992	$98.60	$98.60	$98.60
Purchase #5	$55.93	4.733%	$58.5772	$58.58	$58.60	$58.60
Purchase #6	$221.88	11.460%	$247.3074	$247.31	$247.30	$247.30
Purchase #7	$113.72	3.182%	$117.3386	$117.34	$117.35	$117.30
7 purchase totals =	$752.65		$825.7157	$825.73	$825.75	$825.70