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	$63.90	11.422%	$71.1987	$71.20	$71.20	$71.20
Purchase #2	$7.44	12.822%	$8.394	$8.39	$8.40	$8.40
Purchase #3	$67.39	9.237%	$73.6148	$73.61	$73.60	$73.60
Purchase #4	$227.29	7.250%	$243.7685	$243.77	$243.75	$243.80
Purchase #5	$144.31	3.176%	$148.8933	$148.89	$148.90	$148.90
Purchase #6	$248.62	10.740%	$275.3218	$275.32	$275.30	$275.30
Purchase #7	$245.49	3.840%	$254.9168	$254.92	$254.90	$254.90
7 purchase totals =	$1,004.44		$1,076.1079	$1,076.10	$1,076.05	$1,076.10