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	$66.89	8.300%	$72.4419	$72.44	$72.45	$72.40
Purchase #2	$80.80	5.726%	$85.4266	$85.43	$85.45	$85.40
Purchase #3	$116.67	7.108%	$124.9629	$124.96	$124.95	$125.00
Purchase #4	$229.55	11.429%	$255.7853	$255.79	$255.80	$255.80
Purchase #5	$230.72	10.124%	$254.0781	$254.08	$254.10	$254.10
Purchase #6	$72.81	11.511%	$81.1912	$81.19	$81.20	$81.20
Purchase #7	$75.56	12.791%	$85.2249	$85.22	$85.20	$85.20
7 purchase totals =	$873.00		$959.1109	$959.11	$959.15	$959.10