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	$63.46	13.766%	$72.1959	$72.20	$72.20	$72.20
Purchase #2	$176.66	11.406%	$196.8098	$196.81	$196.80	$196.80
Purchase #3	$42.30	7.465%	$45.4577	$45.46	$45.45	$45.50
Purchase #4	$167.49	4.832%	$175.5831	$175.58	$175.60	$175.60
Purchase #5	$91.83	5.282%	$96.6805	$96.68	$96.70	$96.70
Purchase #6	$81.64	13.384%	$92.5667	$92.57	$92.55	$92.60
Purchase #7	$56.72	7.851%	$61.1731	$61.17	$61.15	$61.20
7 purchase totals =	$680.10		$740.4668	$740.47	$740.45	$740.60