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	$219.25	12.210%	$246.0204	$246.02	$246.00	$246.00
Purchase #2	$81.28	5.696%	$85.9097	$85.91	$85.90	$85.90
Purchase #3	$214.68	13.804%	$244.3144	$244.31	$244.30	$244.30
Purchase #4	$192.64	10.594%	$213.0483	$213.05	$213.05	$213.00
Purchase #5	$201.73	8.772%	$219.4258	$219.43	$219.45	$219.40
Purchase #6	$51.94	3.157%	$53.5797	$53.58	$53.60	$53.60
Purchase #7	$79.88	12.189%	$89.6166	$89.62	$89.60	$89.60
7 purchase totals =	$1,041.40		$1,151.9149	$1,151.92	$1,151.90	$1,151.80