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	$13.61	9.789%	$14.9423	$14.94	$14.95	$14.90
Purchase #2	$98.72	11.812%	$110.3808	$110.38	$110.40	$110.40
Purchase #3	$70.80	11.434%	$78.8953	$78.90	$78.90	$78.90
Purchase #4	$77.50	7.488%	$83.3032	$83.30	$83.30	$83.30
Purchase #5	$124.77	12.336%	$140.1616	$140.16	$140.15	$140.20
Purchase #6	$169.57	4.163%	$176.6292	$176.63	$176.65	$176.60
Purchase #7	$51.65	5.336%	$54.406	$54.41	$54.40	$54.40
7 purchase totals =	$606.62		$658.7184	$658.72	$658.75	$658.70