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	$91.92	4.251%	$95.8275	$95.83	$95.85	$95.80
Purchase #2	$190.86	10.635%	$211.158	$211.16	$211.15	$211.20
Purchase #3	$143.85	11.179%	$159.931	$159.93	$159.95	$159.90
Purchase #4	$64.42	12.406%	$72.4119	$72.41	$72.40	$72.40
Purchase #5	$89.56	3.483%	$92.6794	$92.68	$92.70	$92.70
Purchase #6	$140.95	7.835%	$151.9934	$151.99	$152.00	$152.00
Purchase #7	$141.36	4.431%	$147.6237	$147.62	$147.60	$147.60
7 purchase totals =	$862.92		$931.6249	$931.62	$931.65	$931.60