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	$65.61	5.670%	$69.3301	$69.33	$69.35	$69.30
Purchase #2	$109.85	3.381%	$113.564	$113.56	$113.55	$113.60
Purchase #3	$171.29	11.285%	$190.6201	$190.62	$190.60	$190.60
Purchase #4	$95.70	4.369%	$99.8811	$99.88	$99.90	$99.90
Purchase #5	$19.86	9.588%	$21.7642	$21.76	$21.75	$21.80
Purchase #6	$64.73	11.651%	$72.2717	$72.27	$72.25	$72.30
Purchase #7	$149.70	6.253%	$159.0607	$159.06	$159.05	$159.10
7 purchase totals =	$676.74		$726.4919	$726.48	$726.45	$726.60