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	$177.89	7.126%	$190.5664	$190.57	$190.55	$190.60
Purchase #2	$112.60	6.208%	$119.5902	$119.59	$119.60	$119.60
Purchase #3	$94.63	11.724%	$105.7244	$105.72	$105.70	$105.70
Purchase #4	$59.78	12.518%	$67.2633	$67.26	$67.25	$67.30
Purchase #5	$243.42	11.486%	$271.3792	$271.38	$271.40	$271.40
Purchase #6	$182.30	9.502%	$199.6221	$199.62	$199.60	$199.60
Purchase #7	$65.62	7.410%	$70.4824	$70.48	$70.50	$70.50
7 purchase totals =	$936.24		$1,024.6280	$1,024.62	$1,024.60	$1,024.70