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	$223.93	7.799%	$241.3943	$241.39	$241.40	$241.40
Purchase #2	$78.47	10.873%	$87.002	$87.00	$87.00	$87.00
Purchase #3	$211.56	4.561%	$221.2093	$221.21	$221.20	$221.20
Purchase #4	$57.29	7.433%	$61.5484	$61.55	$61.55	$61.50
Purchase #5	$162.98	10.746%	$180.4938	$180.49	$180.50	$180.50
Purchase #6	$231.71	4.661%	$242.51	$242.51	$242.50	$242.50
Purchase #7	$148.70	5.795%	$157.3172	$157.32	$157.30	$157.30
7 purchase totals =	$1,114.64		$1,191.4750	$1,191.47	$1,191.45	$1,191.40