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	$137.46	3.197%	$141.8546	$141.85	$141.85	$141.90
Purchase #2	$120.69	10.617%	$133.5037	$133.50	$133.50	$133.50
Purchase #3	$55.28	7.537%	$59.4465	$59.45	$59.45	$59.40
Purchase #4	$95.47	6.355%	$101.5371	$101.54	$101.55	$101.50
Purchase #5	$152.32	11.671%	$170.0973	$170.10	$170.10	$170.10
Purchase #6	$66.51	8.479%	$72.1494	$72.15	$72.15	$72.10
Purchase #7	$236.63	11.851%	$264.673	$264.67	$264.65	$264.70
7 purchase totals =	$864.36		$943.2616	$943.26	$943.25	$943.20