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	$44.82	13.476%	$50.8599	$50.86	$50.85	$50.90
Purchase #2	$180.27	6.846%	$192.6113	$192.61	$192.60	$192.60
Purchase #3	$14.99	5.755%	$15.8527	$15.85	$15.85	$15.90
Purchase #4	$152.86	9.361%	$167.1692	$167.17	$167.15	$167.20
Purchase #5	$180.82	8.424%	$196.0523	$196.05	$196.05	$196.10
Purchase #6	$98.97	11.162%	$110.017	$110.02	$110.00	$110.00
Purchase #7	$239.96	13.634%	$272.6761	$272.68	$272.70	$272.70
7 purchase totals =	$912.69		$1,005.2385	$1,005.24	$1,005.20	$1,005.40