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	$186.67	11.679%	$208.4712	$208.47	$208.45	$208.50
Purchase #2	$70.81	12.623%	$79.7483	$79.75	$79.75	$79.70
Purchase #3	$222.33	4.105%	$231.4566	$231.46	$231.45	$231.50
Purchase #4	$232.68	13.479%	$264.0429	$264.04	$264.05	$264.00
Purchase #5	$168.87	13.317%	$191.3584	$191.36	$191.35	$191.40
Purchase #6	$46.96	13.344%	$53.2263	$53.23	$53.25	$53.20
Purchase #7	$60.42	11.861%	$67.5864	$67.59	$67.60	$67.60
7 purchase totals =	$988.74		$1,095.8901	$1,095.90	$1,095.90	$1,095.90