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	$196.64	12.701%	$221.6152	$221.62	$221.60	$221.60
Purchase #2	$58.86	13.675%	$66.9091	$66.91	$66.90	$66.90
Purchase #3	$150.60	10.166%	$165.91	$165.91	$165.90	$165.90
Purchase #4	$211.50	13.713%	$240.503	$240.50	$240.50	$240.50
Purchase #5	$125.36	3.326%	$129.5295	$129.53	$129.55	$129.50
Purchase #6	$212.30	4.243%	$221.3079	$221.31	$221.30	$221.30
Purchase #7	$14.51	9.204%	$15.8455	$15.85	$15.85	$15.80
7 purchase totals =	$969.77		$1,061.6202	$1,061.63	$1,061.60	$1,061.50