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	$145.29	8.287%	$157.3302	$157.33	$157.35	$157.30
Purchase #2	$51.53	8.386%	$55.8513	$55.85	$55.85	$55.90
Purchase #3	$62.51	3.117%	$64.4584	$64.46	$64.45	$64.50
Purchase #4	$160.99	6.106%	$170.82	$170.82	$170.80	$170.80
Purchase #5	$27.27	7.312%	$29.264	$29.26	$29.25	$29.30
Purchase #6	$102.71	6.865%	$109.761	$109.76	$109.75	$109.80
Purchase #7	$54.51	9.105%	$59.4731	$59.47	$59.45	$59.50
7 purchase totals =	$604.81		$646.9580	$646.95	$646.90	$647.10