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	$202.75	13.177%	$229.4664	$229.47	$229.45	$229.50
Purchase #2	$219.44	10.223%	$241.8734	$241.87	$241.85	$241.90
Purchase #3	$192.41	12.707%	$216.8595	$216.86	$216.85	$216.90
Purchase #4	$201.44	6.123%	$213.7742	$213.77	$213.75	$213.80
Purchase #5	$90.60	11.729%	$101.2265	$101.23	$101.25	$101.20
Purchase #6	$84.82	12.735%	$95.6218	$95.62	$95.60	$95.60
Purchase #7	$81.83	10.805%	$90.6717	$90.67	$90.65	$90.70
7 purchase totals =	$1,073.29		$1,189.4935	$1,189.49	$1,189.40	$1,189.60