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	$42.85	3.763%	$44.4624	$44.46	$44.45	$44.50
Purchase #2	$32.88	5.578%	$34.714	$34.71	$34.70	$34.70
Purchase #3	$101.48	4.167%	$105.7087	$105.71	$105.70	$105.70
Purchase #4	$81.25	5.434%	$85.6651	$85.67	$85.65	$85.70
Purchase #5	$156.75	9.633%	$171.8497	$171.85	$171.85	$171.80
Purchase #6	$153.36	8.392%	$166.23	$166.23	$166.25	$166.20
Purchase #7	$74.39	3.589%	$77.0599	$77.06	$77.05	$77.10
7 purchase totals =	$642.96		$685.6898	$685.69	$685.65	$685.70