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	$194.30	12.281%	$218.162	$218.16	$218.15	$218.20
Purchase #2	$62.49	7.488%	$67.1693	$67.17	$67.15	$67.20
Purchase #3	$95.73	9.426%	$104.7535	$104.75	$104.75	$104.80
Purchase #4	$119.29	6.231%	$126.723	$126.72	$126.70	$126.70
Purchase #5	$172.70	10.267%	$190.4311	$190.43	$190.45	$190.40
Purchase #6	$224.53	9.768%	$246.4621	$246.46	$246.45	$246.50
Purchase #7	$82.46	12.471%	$92.7436	$92.74	$92.75	$92.70
7 purchase totals =	$951.50		$1,046.4446	$1,046.43	$1,046.40	$1,046.50