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	$107.32	5.634%	$113.3664	$113.37	$113.35	$113.40
Purchase #2	$52.92	11.507%	$59.0095	$59.01	$59.00	$59.00
Purchase #3	$75.37	11.228%	$83.8325	$83.83	$83.85	$83.80
Purchase #4	$136.89	13.582%	$155.4824	$155.48	$155.50	$155.50
Purchase #5	$216.32	4.353%	$225.7364	$225.74	$225.75	$225.70
Purchase #6	$41.61	10.713%	$46.0677	$46.07	$46.05	$46.10
Purchase #7	$24.55	13.241%	$27.8007	$27.80	$27.80	$27.80
7 purchase totals =	$654.98		$711.2956	$711.30	$711.30	$711.30