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	$48.95	4.660%	$51.2311	$51.23	$51.25	$51.20
Purchase #2	$102.27	12.571%	$115.1264	$115.13	$115.15	$115.10
Purchase #3	$203.86	11.617%	$227.5424	$227.54	$227.55	$227.50
Purchase #4	$27.89	9.504%	$30.5407	$30.54	$30.55	$30.50
Purchase #5	$244.65	8.128%	$264.5352	$264.54	$264.55	$264.50
Purchase #6	$143.86	9.760%	$157.9007	$157.90	$157.90	$157.90
Purchase #7	$222.77	7.527%	$239.5379	$239.54	$239.55	$239.50
7 purchase totals =	$994.25		$1,086.4144	$1,086.42	$1,086.50	$1,086.20