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	$38.37	7.242%	$41.1488	$41.15	$41.15	$41.10
Purchase #2	$83.78	5.802%	$88.6409	$88.64	$88.65	$88.60
Purchase #3	$92.71	8.867%	$100.9306	$100.93	$100.95	$100.90
Purchase #4	$98.73	10.193%	$108.7935	$108.79	$108.80	$108.80
Purchase #5	$126.57	11.178%	$140.718	$140.72	$140.70	$140.70
Purchase #6	$211.75	4.508%	$221.2957	$221.30	$221.30	$221.30
Purchase #7	$50.49	12.523%	$56.8129	$56.81	$56.80	$56.80
7 purchase totals =	$702.40		$758.3404	$758.34	$758.35	$758.20