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	$63.73	12.431%	$71.6523	$71.65	$71.65	$71.70
Purchase #2	$156.64	11.282%	$174.3121	$174.31	$174.30	$174.30
Purchase #3	$37.67	11.652%	$42.0593	$42.06	$42.05	$42.10
Purchase #4	$106.40	12.507%	$119.7074	$119.71	$119.70	$119.70
Purchase #5	$129.64	7.348%	$139.1659	$139.17	$139.15	$139.20
Purchase #6	$11.70	11.462%	$13.0411	$13.04	$13.05	$13.00
Purchase #7	$133.73	8.476%	$145.065	$145.07	$145.05	$145.10
7 purchase totals =	$639.51		$705.0031	$705.01	$704.95	$705.10