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	$104.49	7.337%	$112.1564	$112.16	$112.15	$112.20
Purchase #2	$57.75	10.240%	$63.6636	$63.66	$63.65	$63.70
Purchase #3	$69.96	4.521%	$73.1229	$73.12	$73.10	$73.10
Purchase #4	$63.84	11.300%	$71.0539	$71.05	$71.05	$71.10
Purchase #5	$79.39	13.180%	$89.8536	$89.85	$89.85	$89.90
Purchase #6	$25.82	5.406%	$27.2158	$27.22	$27.20	$27.20
Purchase #7	$76.38	7.162%	$81.8503	$81.85	$81.85	$81.90
7 purchase totals =	$477.63		$518.9165	$518.91	$518.85	$519.10