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	$216.25	8.842%	$235.3708	$235.37	$235.35	$235.40
Purchase #2	$41.29	8.553%	$44.8215	$44.82	$44.80	$44.80
Purchase #3	$207.49	5.777%	$219.4767	$219.48	$219.50	$219.50
Purchase #4	$65.40	9.390%	$71.5411	$71.54	$71.55	$71.50
Purchase #5	$89.72	11.507%	$100.0441	$100.04	$100.05	$100.00
Purchase #6	$12.32	4.555%	$12.8812	$12.88	$12.90	$12.90
Purchase #7	$223.71	6.730%	$238.7657	$238.77	$238.75	$238.80
7 purchase totals =	$856.18		$922.9011	$922.90	$922.90	$922.90