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	$193.99	3.510%	$200.799	$200.80	$200.80	$200.80
Purchase #2	$172.29	8.439%	$186.8296	$186.83	$186.85	$186.80
Purchase #3	$141.28	7.319%	$151.6203	$151.62	$151.60	$151.60
Purchase #4	$96.40	4.593%	$100.8277	$100.83	$100.85	$100.80
Purchase #5	$127.32	10.255%	$140.3767	$140.38	$140.40	$140.40
Purchase #6	$133.60	13.835%	$152.0836	$152.08	$152.10	$152.10
Purchase #7	$249.73	13.123%	$282.5021	$282.50	$282.50	$282.50
7 purchase totals =	$1,114.61		$1,215.0390	$1,215.04	$1,215.10	$1,215.00