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	$34.54	5.361%	$36.3917	$36.39	$36.40	$36.40
Purchase #2	$86.88	6.619%	$92.6306	$92.63	$92.65	$92.60
Purchase #3	$167.91	10.684%	$185.8495	$185.85	$185.85	$185.80
Purchase #4	$47.66	6.468%	$50.7426	$50.74	$50.75	$50.70
Purchase #5	$38.54	5.412%	$40.6258	$40.63	$40.65	$40.60
Purchase #6	$131.27	4.380%	$137.0196	$137.02	$137.00	$137.00
Purchase #7	$190.89	12.344%	$214.4535	$214.45	$214.45	$214.50
7 purchase totals =	$697.69		$757.7133	$757.71	$757.75	$757.60