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	$151.34	4.561%	$158.2426	$158.24	$158.25	$158.20
Purchase #2	$85.96	10.338%	$94.8465	$94.85	$94.85	$94.80
Purchase #3	$22.37	9.780%	$24.5578	$24.56	$24.55	$24.60
Purchase #4	$222.43	8.344%	$240.9896	$240.99	$241.00	$241.00
Purchase #5	$58.50	4.465%	$61.112	$61.11	$61.10	$61.10
Purchase #6	$76.56	11.842%	$85.6262	$85.63	$85.65	$85.60
Purchase #7	$68.84	5.603%	$72.6971	$72.70	$72.70	$72.70
7 purchase totals =	$686.00		$738.0718	$738.08	$738.10	$738.00