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	$164.25	10.372%	$181.286	$181.29	$181.30	$181.30
Purchase #2	$57.43	9.657%	$62.976	$62.98	$63.00	$63.00
Purchase #3	$72.91	12.479%	$82.0084	$82.01	$82.00	$82.00
Purchase #4	$57.51	3.496%	$59.5205	$59.52	$59.50	$59.50
Purchase #5	$228.57	10.461%	$252.4807	$252.48	$252.50	$252.50
Purchase #6	$171.74	5.293%	$180.8302	$180.83	$180.85	$180.80
Purchase #7	$125.31	4.288%	$130.6833	$130.68	$130.70	$130.70
7 purchase totals =	$877.72		$949.7851	$949.79	$949.85	$949.80