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	$173.33	7.235%	$185.8704	$185.87	$185.85	$185.90
Purchase #2	$128.95	6.718%	$137.6129	$137.61	$137.60	$137.60
Purchase #3	$161.55	11.315%	$179.8294	$179.83	$179.85	$179.80
Purchase #4	$163.62	6.290%	$173.9117	$173.91	$173.90	$173.90
Purchase #5	$54.28	9.526%	$59.4507	$59.45	$59.45	$59.50
Purchase #6	$39.97	8.810%	$43.4914	$43.49	$43.50	$43.50
Purchase #7	$23.96	7.863%	$25.844	$25.84	$25.85	$25.80
7 purchase totals =	$745.66		$806.0105	$806.00	$806.00	$806.00