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	$248.31	6.638%	$264.7928	$264.79	$264.80	$264.80
Purchase #2	$8.28	4.387%	$8.6432	$8.64	$8.65	$8.60
Purchase #3	$171.29	7.131%	$183.5047	$183.50	$183.50	$183.50
Purchase #4	$85.95	4.480%	$89.8006	$89.80	$89.80	$89.80
Purchase #5	$22.92	11.684%	$25.598	$25.60	$25.60	$25.60
Purchase #6	$107.89	3.210%	$111.3533	$111.35	$111.35	$111.40
Purchase #7	$171.94	7.417%	$184.6928	$184.69	$184.70	$184.70
7 purchase totals =	$816.58		$868.3854	$868.37	$868.40	$868.40