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	$168.47	9.369%	$184.254	$184.25	$184.25	$184.30
Purchase #2	$121.83	4.390%	$127.1783	$127.18	$127.20	$127.20
Purchase #3	$22.60	12.130%	$25.3414	$25.34	$25.35	$25.30
Purchase #4	$55.95	5.641%	$59.1061	$59.11	$59.10	$59.10
Purchase #5	$37.41	12.159%	$41.9587	$41.96	$41.95	$42.00
Purchase #6	$71.90	13.479%	$81.5914	$81.59	$81.60	$81.60
Purchase #7	$206.84	8.610%	$224.6489	$224.65	$224.65	$224.60
7 purchase totals =	$685.00		$744.0788	$744.08	$744.10	$744.10