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	$173.98	4.580%	$181.9483	$181.95	$181.95	$181.90
Purchase #2	$92.85	4.810%	$97.3161	$97.32	$97.30	$97.30
Purchase #3	$79.77	4.730%	$83.5431	$83.54	$83.55	$83.50
Purchase #4	$65.48	10.468%	$72.3344	$72.33	$72.35	$72.30
Purchase #5	$247.57	13.791%	$281.7124	$281.71	$281.70	$281.70
Purchase #6	$241.79	8.104%	$261.3847	$261.38	$261.40	$261.40
Purchase #7	$241.61	12.620%	$272.1012	$272.10	$272.10	$272.10
7 purchase totals =	$1,143.05		$1,250.3402	$1,250.33	$1,250.35	$1,250.20