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	$85.78	5.488%	$90.4876	$90.49	$90.50	$90.50
Purchase #2	$212.77	6.129%	$225.8107	$225.81	$225.80	$225.80
Purchase #3	$28.77	12.500%	$32.3663	$32.37	$32.35	$32.40
Purchase #4	$192.89	11.387%	$214.8544	$214.85	$214.85	$214.90
Purchase #5	$247.55	6.802%	$264.3884	$264.39	$264.40	$264.40
Purchase #6	$229.57	7.293%	$246.3125	$246.31	$246.30	$246.30
Purchase #7	$208.44	6.136%	$221.2299	$221.23	$221.25	$221.20
7 purchase totals =	$1,205.77		$1,295.4498	$1,295.45	$1,295.45	$1,295.50