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	$22.88	13.421%	$25.9507	$25.95	$25.95	$26.00
Purchase #2	$53.78	13.603%	$61.0957	$61.10	$61.10	$61.10
Purchase #3	$46.39	7.617%	$49.9235	$49.92	$49.90	$49.90
Purchase #4	$231.34	5.534%	$244.1424	$244.14	$244.15	$244.10
Purchase #5	$70.62	3.194%	$72.8756	$72.88	$72.90	$72.90
Purchase #6	$93.67	6.525%	$99.782	$99.78	$99.80	$99.80
Purchase #7	$47.25	7.400%	$50.7465	$50.75	$50.75	$50.70
7 purchase totals =	$565.93		$604.5164	$604.52	$604.55	$604.50