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	$89.70	5.595%	$94.7187	$94.72	$94.70	$94.70
Purchase #2	$108.88	3.682%	$112.889	$112.89	$112.90	$112.90
Purchase #3	$59.67	12.493%	$67.1246	$67.12	$67.10	$67.10
Purchase #4	$33.37	11.252%	$37.1248	$37.12	$37.10	$37.10
Purchase #5	$86.41	7.668%	$93.0359	$93.04	$93.05	$93.00
Purchase #6	$139.79	8.865%	$152.1824	$152.18	$152.20	$152.20
Purchase #7	$154.85	13.572%	$175.8662	$175.87	$175.85	$175.90
7 purchase totals =	$672.67		$732.9416	$732.94	$732.90	$732.90