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	$101.29	10.737%	$112.1655	$112.17	$112.15	$112.20
Purchase #2	$248.26	13.255%	$281.1669	$281.17	$281.15	$281.20
Purchase #3	$92.96	7.421%	$99.8586	$99.86	$99.85	$99.90
Purchase #4	$226.47	5.232%	$238.3189	$238.32	$238.30	$238.30
Purchase #5	$140.37	6.817%	$149.939	$149.94	$149.95	$149.90
Purchase #6	$223.32	3.678%	$231.5337	$231.53	$231.55	$231.50
Purchase #7	$87.39	3.696%	$90.6199	$90.62	$90.60	$90.60
7 purchase totals =	$1,120.06		$1,203.6025	$1,203.61	$1,203.55	$1,203.60