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	$242.33	3.352%	$250.4529	$250.45	$250.45	$250.50
Purchase #2	$188.51	6.392%	$200.5596	$200.56	$200.55	$200.60
Purchase #3	$26.26	5.482%	$27.6996	$27.70	$27.70	$27.70
Purchase #4	$121.86	9.223%	$133.0991	$133.10	$133.10	$133.10
Purchase #5	$236.82	8.482%	$256.9071	$256.91	$256.90	$256.90
Purchase #6	$28.91	10.810%	$32.0352	$32.04	$32.05	$32.00
Purchase #7	$116.56	6.181%	$123.7646	$123.76	$123.75	$123.80
7 purchase totals =	$961.25		$1,024.5181	$1,024.52	$1,024.50	$1,024.60