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	$62.41	8.242%	$67.5538	$67.55	$67.55	$67.60
Purchase #2	$205.54	5.127%	$216.078	$216.08	$216.10	$216.10
Purchase #3	$113.45	12.369%	$127.4826	$127.48	$127.50	$127.50
Purchase #4	$240.53	5.511%	$253.7856	$253.79	$253.80	$253.80
Purchase #5	$35.95	4.283%	$37.4897	$37.49	$37.50	$37.50
Purchase #6	$109.47	6.719%	$116.8253	$116.83	$116.85	$116.80
Purchase #7	$129.76	13.319%	$147.0427	$147.04	$147.05	$147.00
7 purchase totals =	$897.11		$966.2577	$966.26	$966.35	$966.30