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	$203.25	6.673%	$216.8129	$216.81	$216.80	$216.80
Purchase #2	$194.72	8.455%	$211.1836	$211.18	$211.20	$211.20
Purchase #3	$206.30	7.174%	$221.1	$221.10	$221.10	$221.10
Purchase #4	$173.52	13.254%	$196.5183	$196.52	$196.50	$196.50
Purchase #5	$41.96	11.781%	$46.9033	$46.90	$46.90	$46.90
Purchase #6	$62.59	3.167%	$64.5722	$64.57	$64.55	$64.60
Purchase #7	$133.27	13.576%	$151.3627	$151.36	$151.35	$151.40
7 purchase totals =	$1,015.61		$1,108.4530	$1,108.44	$1,108.40	$1,108.50