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	$199.56	8.185%	$215.894	$215.89	$215.90	$215.90
Purchase #2	$76.98	4.510%	$80.4518	$80.45	$80.45	$80.50
Purchase #3	$143.80	5.260%	$151.3639	$151.36	$151.35	$151.40
Purchase #4	$63.71	13.607%	$72.379	$72.38	$72.40	$72.40
Purchase #5	$231.26	6.720%	$246.8007	$246.80	$246.80	$246.80
Purchase #6	$36.40	11.860%	$40.717	$40.72	$40.70	$40.70
Purchase #7	$113.61	9.843%	$124.7926	$124.79	$124.80	$124.80
7 purchase totals =	$865.32		$932.3990	$932.39	$932.40	$932.50