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	$182.69	3.769%	$189.5756	$189.58	$189.60	$189.60
Purchase #2	$41.64	4.660%	$43.5804	$43.58	$43.60	$43.60
Purchase #3	$209.68	10.362%	$231.407	$231.41	$231.40	$231.40
Purchase #4	$37.39	8.623%	$40.6141	$40.61	$40.60	$40.60
Purchase #5	$80.76	10.257%	$89.0436	$89.04	$89.05	$89.00
Purchase #6	$81.73	7.282%	$87.6816	$87.68	$87.70	$87.70
Purchase #7	$31.32	13.161%	$35.442	$35.44	$35.45	$35.40
7 purchase totals =	$665.21		$717.3443	$717.34	$717.40	$717.30