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	$225.71	13.362%	$255.8694	$255.87	$255.85	$255.90
Purchase #2	$215.78	12.418%	$242.5756	$242.58	$242.60	$242.60
Purchase #3	$183.84	3.199%	$189.721	$189.72	$189.70	$189.70
Purchase #4	$71.63	13.353%	$81.1948	$81.19	$81.20	$81.20
Purchase #5	$239.53	6.505%	$255.1114	$255.11	$255.10	$255.10
Purchase #6	$152.76	9.240%	$166.875	$166.88	$166.90	$166.90
Purchase #7	$39.47	7.343%	$42.3683	$42.37	$42.35	$42.40
7 purchase totals =	$1,128.72		$1,233.7155	$1,233.72	$1,233.70	$1,233.80