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	$129.76	3.512%	$134.3172	$134.32	$134.30	$134.30
Purchase #2	$151.93	8.754%	$165.23	$165.23	$165.25	$165.20
Purchase #3	$245.96	11.716%	$274.7767	$274.78	$274.80	$274.80
Purchase #4	$161.48	5.514%	$170.384	$170.38	$170.40	$170.40
Purchase #5	$129.28	10.695%	$143.1065	$143.11	$143.10	$143.10
Purchase #6	$60.45	5.149%	$63.5626	$63.56	$63.55	$63.60
Purchase #7	$68.54	4.348%	$71.5201	$71.52	$71.50	$71.50
7 purchase totals =	$947.40		$1,022.8971	$1,022.90	$1,022.90	$1,022.90