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	$140.37	7.750%	$151.2487	$151.25	$151.25	$151.20
Purchase #2	$229.81	12.488%	$258.5087	$258.51	$258.50	$258.50
Purchase #3	$160.79	5.402%	$169.4759	$169.48	$169.50	$169.50
Purchase #4	$50.52	3.703%	$52.3908	$52.39	$52.40	$52.40
Purchase #5	$135.50	11.753%	$151.4253	$151.43	$151.45	$151.40
Purchase #6	$117.71	9.525%	$128.9219	$128.92	$128.90	$128.90
Purchase #7	$38.91	8.112%	$42.0664	$42.07	$42.05	$42.10
7 purchase totals =	$873.61		$954.0377	$954.05	$954.05	$954.00