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	$39.29	5.511%	$41.4553	$41.46	$41.45	$41.50
Purchase #2	$68.70	3.827%	$71.3291	$71.33	$71.35	$71.30
Purchase #3	$34.98	9.186%	$38.1933	$38.19	$38.20	$38.20
Purchase #4	$35.65	12.612%	$40.1462	$40.15	$40.15	$40.10
Purchase #5	$247.91	12.359%	$278.5492	$278.55	$278.55	$278.50
Purchase #6	$77.82	7.871%	$83.9452	$83.95	$83.95	$83.90
Purchase #7	$147.40	10.224%	$162.4702	$162.47	$162.45	$162.50
7 purchase totals =	$651.75		$716.0885	$716.10	$716.10	$716.00