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	$186.36	13.658%	$211.813	$211.81	$211.80	$211.80
Purchase #2	$81.69	12.624%	$92.0025	$92.00	$92.00	$92.00
Purchase #3	$67.98	5.163%	$71.4898	$71.49	$71.50	$71.50
Purchase #4	$90.36	10.410%	$99.7665	$99.77	$99.75	$99.80
Purchase #5	$143.35	10.706%	$158.6971	$158.70	$158.70	$158.70
Purchase #6	$74.93	10.488%	$82.7887	$82.79	$82.80	$82.80
Purchase #7	$135.77	11.228%	$151.0143	$151.01	$151.00	$151.00
7 purchase totals =	$780.44		$867.5719	$867.57	$867.55	$867.60