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	$56.89	7.277%	$61.0299	$61.03	$61.05	$61.00
Purchase #2	$46.35	4.613%	$48.4881	$48.49	$48.50	$48.50
Purchase #3	$33.74	10.703%	$37.3512	$37.35	$37.35	$37.40
Purchase #4	$85.31	13.168%	$96.5436	$96.54	$96.55	$96.50
Purchase #5	$6.73	5.639%	$7.1095	$7.11	$7.10	$7.10
Purchase #6	$147.66	13.635%	$167.7934	$167.79	$167.80	$167.80
Purchase #7	$40.83	3.697%	$42.3395	$42.34	$42.35	$42.30
7 purchase totals =	$417.51		$460.6552	$460.65	$460.70	$460.60