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	$114.80	13.126%	$129.8686	$129.87	$129.85	$129.90
Purchase #2	$171.25	8.355%	$185.5579	$185.56	$185.55	$185.60
Purchase #3	$64.35	5.577%	$67.9388	$67.94	$67.95	$67.90
Purchase #4	$21.46	4.214%	$22.3643	$22.36	$22.35	$22.40
Purchase #5	$36.86	13.685%	$41.9043	$41.90	$41.90	$41.90
Purchase #6	$86.97	5.228%	$91.5168	$91.52	$91.50	$91.50
Purchase #7	$154.48	7.420%	$165.9424	$165.94	$165.95	$165.90
7 purchase totals =	$650.17		$705.0931	$705.09	$705.05	$705.10