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	$88.68	6.554%	$94.4921	$94.49	$94.50	$94.50
Purchase #2	$128.72	9.217%	$140.5841	$140.58	$140.60	$140.60
Purchase #3	$144.84	4.441%	$151.2723	$151.27	$151.25	$151.30
Purchase #4	$136.25	8.195%	$147.4157	$147.42	$147.40	$147.40
Purchase #5	$11.42	10.151%	$12.5792	$12.58	$12.60	$12.60
Purchase #6	$9.94	9.574%	$10.8917	$10.89	$10.90	$10.90
Purchase #7	$200.49	5.363%	$211.2423	$211.24	$211.25	$211.20
7 purchase totals =	$720.34		$768.4774	$768.47	$768.50	$768.50