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	$85.51	7.361%	$91.8044	$91.80	$91.80	$91.80
Purchase #2	$147.26	3.210%	$151.987	$151.99	$152.00	$152.00
Purchase #3	$80.57	7.402%	$86.5338	$86.53	$86.55	$86.50
Purchase #4	$41.67	4.385%	$43.4972	$43.50	$43.50	$43.50
Purchase #5	$132.27	8.245%	$143.1757	$143.18	$143.20	$143.20
Purchase #6	$77.27	11.725%	$86.3299	$86.33	$86.35	$86.30
Purchase #7	$40.77	5.283%	$42.9239	$42.92	$42.90	$42.90
7 purchase totals =	$605.32		$646.2519	$646.25	$646.30	$646.20