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	$64.44	3.358%	$66.6039	$66.60	$66.60	$66.60
Purchase #2	$102.89	8.171%	$111.2971	$111.30	$111.30	$111.30
Purchase #3	$178.76	13.871%	$203.5558	$203.56	$203.55	$203.60
Purchase #4	$215.77	5.452%	$227.5338	$227.53	$227.55	$227.50
Purchase #5	$239.70	10.213%	$264.1806	$264.18	$264.20	$264.20
Purchase #6	$148.29	7.807%	$159.867	$159.87	$159.85	$159.90
Purchase #7	$106.44	4.352%	$111.0723	$111.07	$111.05	$111.10
7 purchase totals =	$1,056.29		$1,144.1105	$1,144.11	$1,144.10	$1,144.20