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	$229.56	5.344%	$241.8277	$241.83	$241.85	$241.80
Purchase #2	$171.27	5.325%	$180.3901	$180.39	$180.40	$180.40
Purchase #3	$121.46	13.202%	$137.4951	$137.50	$137.50	$137.50
Purchase #4	$148.90	11.820%	$166.5	$166.50	$166.50	$166.50
Purchase #5	$181.51	12.606%	$204.3912	$204.39	$204.40	$204.40
Purchase #6	$173.39	7.786%	$186.8901	$186.89	$186.90	$186.90
Purchase #7	$31.32	13.601%	$35.5798	$35.58	$35.60	$35.60
7 purchase totals =	$1,057.41		$1,153.0740	$1,153.08	$1,153.15	$1,153.10