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	$67.48	3.371%	$69.7548	$69.75	$69.75	$69.80
Purchase #2	$155.32	9.593%	$170.2198	$170.22	$170.20	$170.20
Purchase #3	$233.85	10.706%	$258.886	$258.89	$258.90	$258.90
Purchase #4	$96.53	4.242%	$100.6248	$100.62	$100.60	$100.60
Purchase #5	$140.57	4.457%	$146.8352	$146.84	$146.85	$146.80
Purchase #6	$34.35	12.490%	$38.6403	$38.64	$38.65	$38.60
Purchase #7	$203.37	9.529%	$222.7491	$222.75	$222.75	$222.70
7 purchase totals =	$931.47		$1,007.7100	$1,007.71	$1,007.70	$1,007.60