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	$167.50	12.185%	$187.9099	$187.91	$187.90	$187.90
Purchase #2	$130.95	11.250%	$145.6819	$145.68	$145.70	$145.70
Purchase #3	$20.85	4.554%	$21.7995	$21.80	$21.80	$21.80
Purchase #4	$146.67	12.396%	$164.8512	$164.85	$164.85	$164.90
Purchase #5	$232.86	8.859%	$253.4891	$253.49	$253.50	$253.50
Purchase #6	$213.48	6.570%	$227.5056	$227.51	$227.50	$227.50
Purchase #7	$63.75	12.483%	$71.7079	$71.71	$71.70	$71.70
7 purchase totals =	$976.06		$1,072.9451	$1,072.95	$1,072.95	$1,073.00