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	$57.52	11.143%	$63.9295	$63.93	$63.95	$63.90
Purchase #2	$104.48	10.769%	$115.7315	$115.73	$115.75	$115.70
Purchase #3	$240.95	6.442%	$256.472	$256.47	$256.45	$256.50
Purchase #4	$214.96	13.433%	$243.8356	$243.84	$243.85	$243.80
Purchase #5	$99.88	13.569%	$113.4327	$113.43	$113.45	$113.40
Purchase #6	$77.31	4.239%	$80.5872	$80.59	$80.60	$80.60
Purchase #7	$175.97	11.413%	$196.0535	$196.05	$196.05	$196.10
7 purchase totals =	$971.07		$1,070.0420	$1,070.04	$1,070.10	$1,070.00