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	$142.58	13.819%	$162.2831	$162.28	$162.30	$162.30
Purchase #2	$103.71	10.784%	$114.8941	$114.89	$114.90	$114.90
Purchase #3	$244.55	13.837%	$278.3884	$278.39	$278.40	$278.40
Purchase #4	$149.78	13.343%	$169.7651	$169.77	$169.75	$169.80
Purchase #5	$55.48	3.134%	$57.2187	$57.22	$57.20	$57.20
Purchase #6	$209.68	13.532%	$238.0539	$238.05	$238.05	$238.10
Purchase #7	$26.71	6.661%	$28.4892	$28.49	$28.50	$28.50
7 purchase totals =	$932.49		$1,049.0925	$1,049.09	$1,049.10	$1,049.20