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	$213.85	9.480%	$234.123	$234.12	$234.10	$234.10
Purchase #2	$159.87	3.624%	$165.6637	$165.66	$165.65	$165.70
Purchase #3	$142.52	4.234%	$148.5543	$148.55	$148.55	$148.60
Purchase #4	$100.29	13.361%	$113.6897	$113.69	$113.70	$113.70
Purchase #5	$64.83	12.199%	$72.7386	$72.74	$72.75	$72.70
Purchase #6	$210.55	4.430%	$219.8774	$219.88	$219.90	$219.90
Purchase #7	$42.71	5.483%	$45.0518	$45.05	$45.05	$45.10
7 purchase totals =	$934.62		$999.6985	$999.69	$999.70	$999.80