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	$199.68	13.776%	$227.1879	$227.19	$227.20	$227.20
Purchase #2	$89.89	5.231%	$94.5921	$94.59	$94.60	$94.60
Purchase #3	$194.29	8.678%	$211.1505	$211.15	$211.15	$211.20
Purchase #4	$34.85	9.472%	$38.151	$38.15	$38.15	$38.20
Purchase #5	$155.48	3.118%	$160.3279	$160.33	$160.35	$160.30
Purchase #6	$153.67	5.429%	$162.0127	$162.01	$162.00	$162.00
Purchase #7	$100.32	4.772%	$105.1073	$105.11	$105.10	$105.10
7 purchase totals =	$928.18		$998.5294	$998.53	$998.55	$998.60