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	$81.56	12.161%	$91.4785	$91.48	$91.50	$91.50
Purchase #2	$82.55	13.322%	$93.5473	$93.55	$93.55	$93.50
Purchase #3	$53.47	11.396%	$59.5634	$59.56	$59.55	$59.60
Purchase #4	$10.69	9.870%	$11.7451	$11.75	$11.75	$11.70
Purchase #5	$88.94	7.777%	$95.8569	$95.86	$95.85	$95.90
Purchase #6	$114.31	5.219%	$120.2758	$120.28	$120.30	$120.30
Purchase #7	$205.94	8.600%	$223.6508	$223.65	$223.65	$223.70
7 purchase totals =	$637.46		$696.1178	$696.13	$696.15	$696.20