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	$156.46	5.667%	$165.3266	$165.33	$165.35	$165.30
Purchase #2	$37.53	5.315%	$39.5247	$39.52	$39.50	$39.50
Purchase #3	$68.96	7.583%	$74.1892	$74.19	$74.20	$74.20
Purchase #4	$172.53	6.677%	$184.0498	$184.05	$184.05	$184.00
Purchase #5	$35.76	10.797%	$39.621	$39.62	$39.60	$39.60
Purchase #6	$235.86	8.343%	$255.5378	$255.54	$255.55	$255.50
Purchase #7	$201.70	10.684%	$223.2496	$223.25	$223.25	$223.20
7 purchase totals =	$908.80		$981.4987	$981.50	$981.50	$981.30