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	$8.76	5.714%	$9.2605	$9.26	$9.25	$9.30
Purchase #2	$174.90	12.482%	$196.731	$196.73	$196.75	$196.70
Purchase #3	$177.29	4.812%	$185.8212	$185.82	$185.80	$185.80
Purchase #4	$164.32	5.187%	$172.8433	$172.84	$172.85	$172.80
Purchase #5	$107.73	12.246%	$120.9226	$120.92	$120.90	$120.90
Purchase #6	$189.48	10.733%	$209.8169	$209.82	$209.80	$209.80
Purchase #7	$37.61	11.803%	$42.0491	$42.05	$42.05	$42.00
7 purchase totals =	$860.09		$937.4446	$937.44	$937.40	$937.30