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	$93.51	7.519%	$100.541	$100.54	$100.55	$100.50
Purchase #2	$64.87	3.394%	$67.0717	$67.07	$67.05	$67.10
Purchase #3	$30.35	6.145%	$32.215	$32.22	$32.20	$32.20
Purchase #4	$124.83	6.113%	$132.4609	$132.46	$132.45	$132.50
Purchase #5	$162.65	8.158%	$175.919	$175.92	$175.90	$175.90
Purchase #6	$85.28	4.380%	$89.0153	$89.02	$89.00	$89.00
Purchase #7	$125.80	8.540%	$136.5433	$136.54	$136.55	$136.50
7 purchase totals =	$687.29		$733.7662	$733.77	$733.70	$733.70