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	$190.50	6.674%	$203.214	$203.21	$203.20	$203.20
Purchase #2	$155.83	10.468%	$172.1423	$172.14	$172.15	$172.10
Purchase #3	$203.54	10.635%	$225.1865	$225.19	$225.20	$225.20
Purchase #4	$139.87	5.566%	$147.6552	$147.66	$147.65	$147.70
Purchase #5	$56.52	11.132%	$62.8118	$62.81	$62.80	$62.80
Purchase #6	$174.89	6.217%	$185.7629	$185.76	$185.75	$185.80
Purchase #7	$40.72	13.318%	$46.1431	$46.14	$46.15	$46.10
7 purchase totals =	$961.87		$1,042.9158	$1,042.91	$1,042.90	$1,042.90