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	$39.74	7.742%	$42.8167	$42.82	$42.80	$42.80
Purchase #2	$66.40	8.769%	$72.2226	$72.22	$72.20	$72.20
Purchase #3	$70.98	4.586%	$74.2351	$74.24	$74.25	$74.20
Purchase #4	$221.75	3.651%	$229.8461	$229.85	$229.85	$229.80
Purchase #5	$192.45	4.323%	$200.7696	$200.77	$200.75	$200.80
Purchase #6	$247.40	11.116%	$274.901	$274.90	$274.90	$274.90
Purchase #7	$142.70	8.254%	$154.4785	$154.48	$154.50	$154.50
7 purchase totals =	$981.42		$1,049.2696	$1,049.28	$1,049.25	$1,049.20