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	$149.48	4.514%	$156.2275	$156.23	$156.25	$156.20
Purchase #2	$85.55	5.120%	$89.9302	$89.93	$89.95	$89.90
Purchase #3	$149.55	8.527%	$162.3021	$162.30	$162.30	$162.30
Purchase #4	$247.34	6.680%	$263.8623	$263.86	$263.85	$263.90
Purchase #5	$245.68	3.195%	$253.5295	$253.53	$253.55	$253.50
Purchase #6	$11.74	10.720%	$12.9985	$13.00	$13.00	$13.00
Purchase #7	$33.46	10.861%	$37.0941	$37.09	$37.10	$37.10
7 purchase totals =	$922.80		$975.9442	$975.94	$976.00	$975.90