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	$165.30	3.547%	$171.1632	$171.16	$171.15	$171.20
Purchase #2	$12.95	5.143%	$13.616	$13.62	$13.60	$13.60
Purchase #3	$139.28	13.865%	$158.5912	$158.59	$158.60	$158.60
Purchase #4	$83.39	4.443%	$87.095	$87.10	$87.10	$87.10
Purchase #5	$140.71	4.748%	$147.3909	$147.39	$147.40	$147.40
Purchase #6	$200.88	11.230%	$223.4388	$223.44	$223.45	$223.40
Purchase #7	$10.83	3.757%	$11.2369	$11.24	$11.25	$11.20
7 purchase totals =	$753.34		$812.5320	$812.54	$812.55	$812.50