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	$243.66	6.251%	$258.8912	$258.89	$258.90	$258.90
Purchase #2	$109.40	5.369%	$115.2737	$115.27	$115.25	$115.30
Purchase #3	$231.46	5.205%	$243.5075	$243.51	$243.50	$243.50
Purchase #4	$235.28	3.763%	$244.1336	$244.13	$244.15	$244.10
Purchase #5	$165.83	11.679%	$185.1973	$185.20	$185.20	$185.20
Purchase #6	$245.99	5.218%	$258.8258	$258.83	$258.85	$258.80
Purchase #7	$139.90	5.833%	$148.0604	$148.06	$148.05	$148.10
7 purchase totals =	$1,371.52		$1,453.8895	$1,453.89	$1,453.90	$1,453.90