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	$177.46	4.441%	$185.341	$185.34	$185.35	$185.30
Purchase #2	$100.98	7.112%	$108.1617	$108.16	$108.15	$108.20
Purchase #3	$79.82	3.849%	$82.8923	$82.89	$82.90	$82.90
Purchase #4	$213.94	12.586%	$240.8665	$240.87	$240.85	$240.90
Purchase #5	$122.43	13.167%	$138.5504	$138.55	$138.55	$138.60
Purchase #6	$64.29	5.540%	$67.8517	$67.85	$67.85	$67.90
Purchase #7	$58.67	5.141%	$61.6862	$61.69	$61.70	$61.70
7 purchase totals =	$817.59		$885.3498	$885.35	$885.35	$885.50