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	$179.35	11.398%	$199.7923	$199.79	$199.80	$199.80
Purchase #2	$10.28	4.305%	$10.7226	$10.72	$10.70	$10.70
Purchase #3	$37.45	7.104%	$40.1104	$40.11	$40.10	$40.10
Purchase #4	$80.84	11.872%	$90.4373	$90.44	$90.45	$90.40
Purchase #5	$117.43	11.157%	$130.5317	$130.53	$130.55	$130.50
Purchase #6	$39.87	11.768%	$44.5619	$44.56	$44.55	$44.60
Purchase #7	$82.79	12.103%	$92.8101	$92.81	$92.80	$92.80
7 purchase totals =	$548.01		$608.9663	$608.96	$608.95	$608.90