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	$190.80	11.589%	$212.9118	$212.91	$212.90	$212.90
Purchase #2	$32.41	11.246%	$36.0548	$36.05	$36.05	$36.10
Purchase #3	$164.86	12.499%	$185.4659	$185.47	$185.45	$185.50
Purchase #4	$223.89	11.725%	$250.1411	$250.14	$250.15	$250.10
Purchase #5	$218.77	4.869%	$229.4219	$229.42	$229.40	$229.40
Purchase #6	$36.78	11.605%	$41.0483	$41.05	$41.05	$41.00
Purchase #7	$230.51	3.174%	$237.8264	$237.83	$237.85	$237.80
7 purchase totals =	$1,098.02		$1,192.8702	$1,192.87	$1,192.85	$1,192.80