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	$78.93	8.158%	$85.3691	$85.37	$85.35	$85.40
Purchase #2	$171.53	6.503%	$182.6846	$182.68	$182.70	$182.70
Purchase #3	$221.58	11.389%	$246.8157	$246.82	$246.80	$246.80
Purchase #4	$159.37	11.731%	$178.0657	$178.07	$178.05	$178.10
Purchase #5	$81.32	9.649%	$89.1666	$89.17	$89.15	$89.20
Purchase #6	$211.86	3.456%	$219.1819	$219.18	$219.20	$219.20
Purchase #7	$86.76	9.259%	$94.7931	$94.79	$94.80	$94.80
7 purchase totals =	$1,011.35		$1,096.0767	$1,096.08	$1,096.05	$1,096.20