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	$37.84	9.211%	$41.3254	$41.33	$41.35	$41.30
Purchase #2	$154.50	4.570%	$161.5607	$161.56	$161.55	$161.60
Purchase #3	$38.72	3.840%	$40.2068	$40.21	$40.20	$40.20
Purchase #4	$59.40	5.524%	$62.6813	$62.68	$62.70	$62.70
Purchase #5	$69.61	12.259%	$78.1435	$78.14	$78.15	$78.10
Purchase #6	$177.48	7.841%	$191.3962	$191.40	$191.40	$191.40
Purchase #7	$152.76	9.502%	$167.2753	$167.28	$167.30	$167.30
7 purchase totals =	$690.31		$742.5892	$742.60	$742.65	$742.60