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	$34.46	9.320%	$37.6717	$37.67	$37.65	$37.70
Purchase #2	$40.48	5.128%	$42.5558	$42.56	$42.55	$42.60
Purchase #3	$157.86	7.373%	$169.499	$169.50	$169.50	$169.50
Purchase #4	$211.82	11.461%	$236.0967	$236.10	$236.10	$236.10
Purchase #5	$18.69	9.626%	$20.4891	$20.49	$20.50	$20.50
Purchase #6	$169.38	11.105%	$188.1896	$188.19	$188.20	$188.20
Purchase #7	$190.53	11.130%	$211.736	$211.74	$211.75	$211.70
7 purchase totals =	$823.22		$906.2379	$906.25	$906.25	$906.30