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	$7.58	11.408%	$8.4447	$8.44	$8.45	$8.40
Purchase #2	$188.62	4.180%	$196.5043	$196.50	$196.50	$196.50
Purchase #3	$209.49	7.721%	$225.6647	$225.66	$225.65	$225.70
Purchase #4	$170.56	8.829%	$185.6187	$185.62	$185.60	$185.60
Purchase #5	$155.51	10.516%	$171.8634	$171.86	$171.85	$171.90
Purchase #6	$112.88	11.487%	$125.8465	$125.85	$125.85	$125.80
Purchase #7	$89.99	11.750%	$100.5638	$100.56	$100.55	$100.60
7 purchase totals =	$934.63		$1,014.5061	$1,014.49	$1,014.45	$1,014.50