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	$105.26	13.637%	$119.6143	$119.61	$119.60	$119.60
Purchase #2	$113.86	13.787%	$129.5579	$129.56	$129.55	$129.60
Purchase #3	$144.89	9.307%	$158.3749	$158.37	$158.35	$158.40
Purchase #4	$248.92	12.793%	$280.7643	$280.76	$280.75	$280.80
Purchase #5	$12.38	6.810%	$13.2231	$13.22	$13.20	$13.20
Purchase #6	$214.94	8.140%	$232.4361	$232.44	$232.45	$232.40
Purchase #7	$55.82	12.672%	$62.8935	$62.89	$62.90	$62.90
7 purchase totals =	$896.07		$996.8641	$996.85	$996.80	$996.90