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	$199.39	8.849%	$217.034	$217.03	$217.05	$217.00
Purchase #2	$112.92	9.213%	$123.3233	$123.32	$123.30	$123.30
Purchase #3	$158.60	11.858%	$177.4068	$177.41	$177.40	$177.40
Purchase #4	$59.36	9.139%	$64.7849	$64.78	$64.80	$64.80
Purchase #5	$147.38	11.665%	$164.5719	$164.57	$164.55	$164.60
Purchase #6	$120.42	13.386%	$136.5394	$136.54	$136.55	$136.50
Purchase #7	$55.78	5.462%	$58.8267	$58.83	$58.85	$58.80
7 purchase totals =	$853.85		$942.4870	$942.48	$942.50	$942.40