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	$213.55	7.484%	$229.5321	$229.53	$229.55	$229.50
Purchase #2	$78.54	5.588%	$82.9288	$82.93	$82.95	$82.90
Purchase #3	$248.33	6.258%	$263.8705	$263.87	$263.85	$263.90
Purchase #4	$214.51	5.843%	$227.0438	$227.04	$227.05	$227.00
Purchase #5	$25.44	10.397%	$28.085	$28.09	$28.10	$28.10
Purchase #6	$168.25	13.533%	$191.0193	$191.02	$191.00	$191.00
Purchase #7	$45.93	5.551%	$48.4796	$48.48	$48.50	$48.50
7 purchase totals =	$994.55		$1,070.9591	$1,070.96	$1,071.00	$1,070.90