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	$132.66	11.387%	$147.766	$147.77	$147.75	$147.80
Purchase #2	$31.78	5.214%	$33.437	$33.44	$33.45	$33.40
Purchase #3	$222.41	12.228%	$249.6063	$249.61	$249.60	$249.60
Purchase #4	$21.82	10.709%	$24.1567	$24.16	$24.15	$24.20
Purchase #5	$21.33	6.666%	$22.7519	$22.75	$22.75	$22.80
Purchase #6	$141.52	8.844%	$154.036	$154.04	$154.05	$154.00
Purchase #7	$37.86	13.749%	$43.0654	$43.07	$43.05	$43.10
7 purchase totals =	$609.38		$674.8193	$674.84	$674.80	$674.90