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	$216.33	9.421%	$236.7104	$236.71	$236.70	$236.70
Purchase #2	$48.65	10.178%	$53.6016	$53.60	$53.60	$53.60
Purchase #3	$78.30	5.735%	$82.7905	$82.79	$82.80	$82.80
Purchase #4	$166.48	5.586%	$175.7796	$175.78	$175.80	$175.80
Purchase #5	$37.46	11.635%	$41.8185	$41.82	$41.80	$41.80
Purchase #6	$55.34	11.853%	$61.8995	$61.90	$61.90	$61.90
Purchase #7	$202.29	7.558%	$217.5791	$217.58	$217.60	$217.60
7 purchase totals =	$804.85		$870.1792	$870.18	$870.20	$870.20