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	$64.44	9.259%	$70.4065	$70.41	$70.40	$70.40
Purchase #2	$49.89	11.560%	$55.6573	$55.66	$55.65	$55.70
Purchase #3	$200.44	11.198%	$222.8853	$222.89	$222.90	$222.90
Purchase #4	$215.96	4.389%	$225.4385	$225.44	$225.45	$225.40
Purchase #5	$42.25	4.394%	$44.1065	$44.11	$44.10	$44.10
Purchase #6	$12.30	3.181%	$12.6913	$12.69	$12.70	$12.70
Purchase #7	$71.89	4.513%	$75.1344	$75.13	$75.15	$75.10
7 purchase totals =	$657.17		$706.3198	$706.33	$706.35	$706.30