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	$182.54	10.607%	$201.902	$201.90	$201.90	$201.90
Purchase #2	$102.77	8.109%	$111.1036	$111.10	$111.10	$111.10
Purchase #3	$161.63	6.486%	$172.1133	$172.11	$172.10	$172.10
Purchase #4	$45.35	11.773%	$50.6891	$50.69	$50.70	$50.70
Purchase #5	$41.49	10.672%	$45.9178	$45.92	$45.90	$45.90
Purchase #6	$147.93	12.112%	$165.8473	$165.85	$165.85	$165.80
Purchase #7	$51.96	10.638%	$57.4875	$57.49	$57.50	$57.50
7 purchase totals =	$733.67		$805.0606	$805.06	$805.05	$805.00