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	$172.93	7.238%	$185.4467	$185.45	$185.45	$185.40
Purchase #2	$247.43	11.369%	$275.5603	$275.56	$275.55	$275.60
Purchase #3	$245.94	5.605%	$259.7249	$259.72	$259.70	$259.70
Purchase #4	$181.26	10.619%	$200.508	$200.51	$200.50	$200.50
Purchase #5	$226.51	6.203%	$240.5604	$240.56	$240.55	$240.60
Purchase #6	$18.72	11.539%	$20.8801	$20.88	$20.90	$20.90
Purchase #7	$233.92	4.525%	$244.5049	$244.50	$244.50	$244.50
7 purchase totals =	$1,326.71		$1,427.1853	$1,427.18	$1,427.15	$1,427.20