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	$50.30	5.776%	$53.2053	$53.21	$53.20	$53.20
Purchase #2	$35.35	7.152%	$37.8782	$37.88	$37.90	$37.90
Purchase #3	$151.82	8.512%	$164.7429	$164.74	$164.75	$164.70
Purchase #4	$61.67	3.643%	$63.9166	$63.92	$63.90	$63.90
Purchase #5	$12.49	12.772%	$14.0852	$14.09	$14.10	$14.10
Purchase #6	$29.73	12.139%	$33.3389	$33.34	$33.35	$33.30
Purchase #7	$190.92	9.507%	$209.0708	$209.07	$209.05	$209.10
7 purchase totals =	$532.28		$576.2379	$576.25	$576.25	$576.20