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	$186.59	5.855%	$197.5148	$197.51	$197.50	$197.50
Purchase #2	$135.99	3.214%	$140.3607	$140.36	$140.35	$140.40
Purchase #3	$103.89	7.303%	$111.4771	$111.48	$111.50	$111.50
Purchase #4	$54.29	9.830%	$59.6267	$59.63	$59.65	$59.60
Purchase #5	$132.63	6.431%	$141.1594	$141.16	$141.15	$141.20
Purchase #6	$30.47	9.818%	$33.4615	$33.46	$33.45	$33.50
Purchase #7	$113.97	8.337%	$123.4717	$123.47	$123.45	$123.50
7 purchase totals =	$757.83		$807.0719	$807.07	$807.05	$807.20