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	$99.78	11.757%	$111.5111	$111.51	$111.50	$111.50
Purchase #2	$168.51	13.675%	$191.5537	$191.55	$191.55	$191.60
Purchase #3	$238.82	3.635%	$247.5011	$247.50	$247.50	$247.50
Purchase #4	$199.91	12.361%	$224.6209	$224.62	$224.60	$224.60
Purchase #5	$119.33	5.491%	$125.8824	$125.88	$125.90	$125.90
Purchase #6	$109.78	8.706%	$119.3374	$119.34	$119.35	$119.30
Purchase #7	$138.26	8.526%	$150.048	$150.05	$150.05	$150.00
7 purchase totals =	$1,074.39		$1,170.4546	$1,170.45	$1,170.45	$1,170.40