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	$7.61	4.159%	$7.9265	$7.93	$7.95	$7.90
Purchase #2	$97.91	11.327%	$109.0003	$109.00	$109.00	$109.00
Purchase #3	$153.54	4.613%	$160.6228	$160.62	$160.60	$160.60
Purchase #4	$227.96	7.758%	$245.6451	$245.65	$245.65	$245.60
Purchase #5	$241.26	13.868%	$274.7179	$274.72	$274.70	$274.70
Purchase #6	$151.72	13.702%	$172.5087	$172.51	$172.50	$172.50
Purchase #7	$41.73	9.624%	$45.7461	$45.75	$45.75	$45.70
7 purchase totals =	$921.73		$1,016.1674	$1,016.18	$1,016.15	$1,016.00