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	$89.97	12.761%	$101.4511	$101.45	$101.45	$101.50
Purchase #2	$207.71	12.109%	$232.8616	$232.86	$232.85	$232.90
Purchase #3	$138.86	3.729%	$144.0381	$144.04	$144.05	$144.00
Purchase #4	$123.29	11.419%	$137.3685	$137.37	$137.35	$137.40
Purchase #5	$235.29	5.218%	$247.5674	$247.57	$247.55	$247.60
Purchase #6	$10.41	13.869%	$11.8538	$11.85	$11.85	$11.90
Purchase #7	$171.36	7.812%	$184.7466	$184.75	$184.75	$184.70
7 purchase totals =	$976.89		$1,059.8871	$1,059.89	$1,059.85	$1,060.00