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	$184.54	5.355%	$194.4221	$194.42	$194.40	$194.40
Purchase #2	$40.44	4.507%	$42.2626	$42.26	$42.25	$42.30
Purchase #3	$128.90	10.196%	$142.0426	$142.04	$142.05	$142.00
Purchase #4	$131.67	6.205%	$139.8401	$139.84	$139.85	$139.80
Purchase #5	$96.40	9.548%	$105.6043	$105.60	$105.60	$105.60
Purchase #6	$66.33	13.499%	$75.2839	$75.28	$75.30	$75.30
Purchase #7	$113.40	3.238%	$117.0719	$117.07	$117.05	$117.10
7 purchase totals =	$761.68		$816.5275	$816.51	$816.50	$816.50