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	$20.66	11.607%	$23.058	$23.06	$23.05	$23.10
Purchase #2	$35.97	10.814%	$39.8598	$39.86	$39.85	$39.90
Purchase #3	$225.72	7.812%	$243.3532	$243.35	$243.35	$243.40
Purchase #4	$43.65	4.313%	$45.5326	$45.53	$45.55	$45.50
Purchase #5	$40.91	3.352%	$42.2813	$42.28	$42.30	$42.30
Purchase #6	$239.80	6.845%	$256.2143	$256.21	$256.20	$256.20
Purchase #7	$37.60	9.298%	$41.096	$41.10	$41.10	$41.10
7 purchase totals =	$644.31		$691.3952	$691.39	$691.40	$691.50