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	$88.51	9.145%	$96.6042	$96.60	$96.60	$96.60
Purchase #2	$38.43	11.438%	$42.8256	$42.83	$42.85	$42.80
Purchase #3	$26.62	7.225%	$28.5433	$28.54	$28.55	$28.50
Purchase #4	$71.86	7.592%	$77.3156	$77.32	$77.30	$77.30
Purchase #5	$37.87	4.141%	$39.4382	$39.44	$39.45	$39.40
Purchase #6	$96.69	8.767%	$105.1668	$105.17	$105.15	$105.20
Purchase #7	$50.37	13.582%	$57.2113	$57.21	$57.20	$57.20
7 purchase totals =	$410.35		$447.1050	$447.11	$447.10	$447.00