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	$231.62	10.153%	$255.1364	$255.14	$255.15	$255.10
Purchase #2	$28.64	5.120%	$30.1064	$30.11	$30.10	$30.10
Purchase #3	$185.42	5.369%	$195.3752	$195.38	$195.40	$195.40
Purchase #4	$244.82	12.494%	$275.4078	$275.41	$275.40	$275.40
Purchase #5	$58.88	9.822%	$64.6632	$64.66	$64.65	$64.70
Purchase #6	$72.78	6.536%	$77.5369	$77.54	$77.55	$77.50
Purchase #7	$121.90	4.224%	$127.0491	$127.05	$127.05	$127.00
7 purchase totals =	$944.06		$1,025.2750	$1,025.29	$1,025.30	$1,025.20