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	$78.68	4.600%	$82.2993	$82.30	$82.30	$82.30
Purchase #2	$28.90	8.124%	$31.2478	$31.25	$31.25	$31.20
Purchase #3	$147.30	9.522%	$161.3259	$161.33	$161.35	$161.30
Purchase #4	$36.67	10.688%	$40.5893	$40.59	$40.60	$40.60
Purchase #5	$72.49	11.576%	$80.8814	$80.88	$80.90	$80.90
Purchase #6	$53.89	4.729%	$56.4385	$56.44	$56.45	$56.40
Purchase #7	$106.51	11.420%	$118.6734	$118.67	$118.65	$118.70
7 purchase totals =	$524.44		$571.4556	$571.46	$571.50	$571.40