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	$65.30	8.674%	$70.9641	$70.96	$70.95	$71.00
Purchase #2	$85.29	3.669%	$88.4193	$88.42	$88.40	$88.40
Purchase #3	$35.39	4.563%	$37.0048	$37.00	$37.00	$37.00
Purchase #4	$175.78	11.571%	$196.1195	$196.12	$196.10	$196.10
Purchase #5	$144.59	8.828%	$157.3544	$157.35	$157.35	$157.40
Purchase #6	$180.96	9.624%	$198.3756	$198.38	$198.40	$198.40
Purchase #7	$140.74	13.785%	$160.141	$160.14	$160.15	$160.10
7 purchase totals =	$828.05		$908.3787	$908.37	$908.35	$908.40