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	$77.61	5.295%	$81.7194	$81.72	$81.70	$81.70
Purchase #2	$234.93	7.232%	$251.9201	$251.92	$251.90	$251.90
Purchase #3	$45.69	10.611%	$50.5382	$50.54	$50.55	$50.50
Purchase #4	$244.37	4.754%	$255.9873	$255.99	$256.00	$256.00
Purchase #5	$169.73	12.804%	$191.4622	$191.46	$191.45	$191.50
Purchase #6	$40.51	10.718%	$44.8519	$44.85	$44.85	$44.90
Purchase #7	$170.33	8.679%	$185.1129	$185.11	$185.10	$185.10
7 purchase totals =	$983.17		$1,061.5920	$1,061.59	$1,061.55	$1,061.60