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	$210.74	4.727%	$220.7017	$220.70	$220.70	$220.70
Purchase #2	$55.31	10.222%	$60.9638	$60.96	$60.95	$61.00
Purchase #3	$242.38	3.561%	$251.0112	$251.01	$251.00	$251.00
Purchase #4	$137.95	9.740%	$151.3863	$151.39	$151.40	$151.40
Purchase #5	$236.86	5.340%	$249.5083	$249.51	$249.50	$249.50
Purchase #6	$72.88	7.398%	$78.2717	$78.27	$78.25	$78.30
Purchase #7	$145.85	4.619%	$152.5868	$152.59	$152.60	$152.60
7 purchase totals =	$1,101.97		$1,164.4298	$1,164.43	$1,164.40	$1,164.50