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	$61.81	8.600%	$67.1257	$67.13	$67.15	$67.10
Purchase #2	$154.48	9.692%	$169.4522	$169.45	$169.45	$169.50
Purchase #3	$240.91	13.779%	$274.105	$274.11	$274.10	$274.10
Purchase #4	$11.79	8.642%	$12.8089	$12.81	$12.80	$12.80
Purchase #5	$235.52	6.324%	$250.4143	$250.41	$250.40	$250.40
Purchase #6	$111.29	8.294%	$120.5204	$120.52	$120.50	$120.50
Purchase #7	$113.43	6.192%	$120.4536	$120.45	$120.45	$120.50
7 purchase totals =	$929.23		$1,014.8801	$1,014.88	$1,014.85	$1,014.90