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	$136.48	7.605%	$146.8593	$146.86	$146.85	$146.90
Purchase #2	$134.73	10.520%	$148.9036	$148.90	$148.90	$148.90
Purchase #3	$43.55	6.642%	$46.4426	$46.44	$46.45	$46.40
Purchase #4	$96.67	13.714%	$109.9273	$109.93	$109.95	$109.90
Purchase #5	$144.30	5.230%	$151.8469	$151.85	$151.85	$151.80
Purchase #6	$89.60	13.596%	$101.782	$101.78	$101.80	$101.80
Purchase #7	$113.42	3.339%	$117.2071	$117.21	$117.20	$117.20
7 purchase totals =	$758.75		$822.9688	$822.97	$823.00	$822.90