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	$73.55	11.576%	$82.0641	$82.06	$82.05	$82.10
Purchase #2	$62.93	10.325%	$69.4275	$69.43	$69.45	$69.40
Purchase #3	$152.56	3.381%	$157.7181	$157.72	$157.70	$157.70
Purchase #4	$71.38	11.569%	$79.638	$79.64	$79.65	$79.60
Purchase #5	$141.56	6.712%	$151.0615	$151.06	$151.05	$151.10
Purchase #6	$111.57	10.326%	$123.0907	$123.09	$123.10	$123.10
Purchase #7	$32.62	6.641%	$34.7863	$34.79	$34.80	$34.80
7 purchase totals =	$646.17		$697.7862	$697.79	$697.80	$697.80