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	$199.89	13.673%	$227.221	$227.22	$227.20	$227.20
Purchase #2	$36.94	12.109%	$41.4131	$41.41	$41.40	$41.40
Purchase #3	$32.56	4.717%	$34.0959	$34.10	$34.10	$34.10
Purchase #4	$210.74	3.817%	$218.7839	$218.78	$218.80	$218.80
Purchase #5	$159.69	4.864%	$167.4573	$167.46	$167.45	$167.50
Purchase #6	$168.55	10.778%	$186.7163	$186.72	$186.70	$186.70
Purchase #7	$66.80	7.300%	$71.6764	$71.68	$71.70	$71.70
7 purchase totals =	$875.17		$947.3639	$947.37	$947.35	$947.40