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	$182.84	8.360%	$198.1254	$198.13	$198.15	$198.10
Purchase #2	$10.64	8.453%	$11.5394	$11.54	$11.55	$11.50
Purchase #3	$227.78	5.160%	$239.5334	$239.53	$239.55	$239.50
Purchase #4	$198.72	13.388%	$225.3246	$225.32	$225.30	$225.30
Purchase #5	$78.28	3.488%	$81.0104	$81.01	$81.00	$81.00
Purchase #6	$42.31	7.477%	$45.4735	$45.47	$45.45	$45.50
Purchase #7	$40.96	13.345%	$46.4261	$46.43	$46.45	$46.40
7 purchase totals =	$781.53		$847.4328	$847.43	$847.45	$847.30