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	$190.57	9.438%	$208.556	$208.56	$208.55	$208.60
Purchase #2	$185.56	13.800%	$211.1673	$211.17	$211.15	$211.20
Purchase #3	$201.90	10.282%	$222.6594	$222.66	$222.65	$222.70
Purchase #4	$157.77	8.457%	$171.1126	$171.11	$171.10	$171.10
Purchase #5	$46.78	9.347%	$51.1525	$51.15	$51.15	$51.20
Purchase #6	$247.71	5.614%	$261.6164	$261.62	$261.60	$261.60
Purchase #7	$46.58	13.571%	$52.9014	$52.90	$52.90	$52.90
7 purchase totals =	$1,076.87		$1,179.1656	$1,179.17	$1,179.10	$1,179.30