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	$136.95	9.498%	$149.9575	$149.96	$149.95	$150.00
Purchase #2	$37.55	9.455%	$41.1004	$41.10	$41.10	$41.10
Purchase #3	$41.36	10.687%	$45.7801	$45.78	$45.80	$45.80
Purchase #4	$153.65	12.563%	$172.953	$172.95	$172.95	$173.00
Purchase #5	$241.43	6.334%	$256.7222	$256.72	$256.70	$256.70
Purchase #6	$176.89	6.588%	$188.5435	$188.54	$188.55	$188.50
Purchase #7	$218.78	9.723%	$240.052	$240.05	$240.05	$240.10
7 purchase totals =	$1,006.61		$1,095.1087	$1,095.10	$1,095.10	$1,095.20