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	$164.63	3.600%	$170.5567	$170.56	$170.55	$170.60
Purchase #2	$5.55	12.830%	$6.2621	$6.26	$6.25	$6.30
Purchase #3	$141.72	9.667%	$155.4201	$155.42	$155.40	$155.40
Purchase #4	$194.36	7.569%	$209.0711	$209.07	$209.05	$209.10
Purchase #5	$78.78	6.119%	$83.6005	$83.60	$83.60	$83.60
Purchase #6	$69.75	12.114%	$78.1995	$78.20	$78.20	$78.20
Purchase #7	$37.67	3.181%	$38.8683	$38.87	$38.85	$38.90
7 purchase totals =	$692.46		$741.9783	$741.98	$741.90	$742.10