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	$213.74	11.742%	$238.8374	$238.84	$238.85	$238.80
Purchase #2	$23.48	8.510%	$25.4781	$25.48	$25.50	$25.50
Purchase #3	$83.54	13.804%	$95.0719	$95.07	$95.05	$95.10
Purchase #4	$111.68	4.675%	$116.901	$116.90	$116.90	$116.90
Purchase #5	$59.78	12.834%	$67.4522	$67.45	$67.45	$67.50
Purchase #6	$52.99	11.625%	$59.1501	$59.15	$59.15	$59.20
Purchase #7	$195.26	8.239%	$211.3475	$211.35	$211.35	$211.30
7 purchase totals =	$740.47		$814.2382	$814.24	$814.25	$814.30