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	$61.25	7.435%	$65.8039	$65.80	$65.80	$65.80
Purchase #2	$6.95	7.235%	$7.4528	$7.45	$7.45	$7.50
Purchase #3	$209.77	8.823%	$228.278	$228.28	$228.30	$228.30
Purchase #4	$137.53	4.372%	$143.5428	$143.54	$143.55	$143.50
Purchase #5	$80.33	3.328%	$83.0034	$83.00	$83.00	$83.00
Purchase #6	$35.75	12.193%	$40.109	$40.11	$40.10	$40.10
Purchase #7	$53.25	3.250%	$54.9806	$54.98	$55.00	$55.00
7 purchase totals =	$584.83		$623.1705	$623.16	$623.20	$623.20