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	$119.70	9.299%	$130.8309	$130.83	$130.85	$130.80
Purchase #2	$6.49	11.411%	$7.2306	$7.23	$7.25	$7.20
Purchase #3	$55.40	11.126%	$61.5638	$61.56	$61.55	$61.60
Purchase #4	$196.65	12.386%	$221.0071	$221.01	$221.00	$221.00
Purchase #5	$37.53	4.338%	$39.1581	$39.16	$39.15	$39.20
Purchase #6	$128.93	4.129%	$134.2535	$134.25	$134.25	$134.30
Purchase #7	$66.42	9.402%	$72.6648	$72.66	$72.65	$72.70
7 purchase totals =	$611.12		$666.7088	$666.70	$666.70	$666.80