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	$62.52	7.653%	$67.3047	$67.30	$67.30	$67.30
Purchase #2	$75.33	5.579%	$79.5327	$79.53	$79.55	$79.50
Purchase #3	$69.41	12.592%	$78.1501	$78.15	$78.15	$78.20
Purchase #4	$118.66	10.196%	$130.7586	$130.76	$130.75	$130.80
Purchase #5	$13.82	9.549%	$15.1397	$15.14	$15.15	$15.10
Purchase #6	$130.73	9.650%	$143.3454	$143.35	$143.35	$143.30
Purchase #7	$33.67	4.238%	$35.0969	$35.10	$35.10	$35.10
7 purchase totals =	$504.14		$549.3281	$549.33	$549.35	$549.30