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	$142.32	13.427%	$161.4293	$161.43	$161.45	$161.40
Purchase #2	$152.69	8.455%	$165.5999	$165.60	$165.60	$165.60
Purchase #3	$53.46	11.446%	$59.579	$59.58	$59.60	$59.60
Purchase #4	$30.37	6.380%	$32.3076	$32.31	$32.30	$32.30
Purchase #5	$28.99	8.325%	$31.4034	$31.40	$31.40	$31.40
Purchase #6	$121.76	4.430%	$127.154	$127.15	$127.15	$127.20
Purchase #7	$31.78	3.742%	$32.9692	$32.97	$32.95	$33.00
7 purchase totals =	$561.37		$610.4424	$610.44	$610.45	$610.50