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	$162.78	3.610%	$168.6564	$168.66	$168.65	$168.70
Purchase #2	$86.83	3.297%	$89.6928	$89.69	$89.70	$89.70
Purchase #3	$130.46	6.412%	$138.8251	$138.83	$138.85	$138.80
Purchase #4	$44.65	11.338%	$49.7124	$49.71	$49.70	$49.70
Purchase #5	$170.81	11.201%	$189.9424	$189.94	$189.95	$189.90
Purchase #6	$218.88	8.836%	$238.2202	$238.22	$238.20	$238.20
Purchase #7	$131.86	12.598%	$148.4717	$148.47	$148.45	$148.50
7 purchase totals =	$946.27		$1,023.5210	$1,023.52	$1,023.50	$1,023.50