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	$193.80	7.221%	$207.7943	$207.79	$207.80	$207.80
Purchase #2	$34.51	9.391%	$37.7508	$37.75	$37.75	$37.80
Purchase #3	$114.33	10.670%	$126.529	$126.53	$126.55	$126.50
Purchase #4	$233.34	13.788%	$265.5129	$265.51	$265.50	$265.50
Purchase #5	$133.90	7.415%	$143.8287	$143.83	$143.85	$143.80
Purchase #6	$75.76	9.563%	$83.0049	$83.00	$83.00	$83.00
Purchase #7	$100.51	11.150%	$111.7169	$111.72	$111.70	$111.70
7 purchase totals =	$886.15		$976.1375	$976.13	$976.15	$976.10