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	$96.61	9.270%	$105.5657	$105.57	$105.55	$105.60
Purchase #2	$234.85	7.105%	$251.5361	$251.54	$251.55	$251.50
Purchase #3	$32.32	3.117%	$33.3274	$33.33	$33.35	$33.30
Purchase #4	$236.47	12.836%	$266.8233	$266.82	$266.80	$266.80
Purchase #5	$136.29	8.202%	$147.4685	$147.47	$147.45	$147.50
Purchase #6	$131.49	10.141%	$144.8244	$144.82	$144.80	$144.80
Purchase #7	$77.30	11.491%	$86.1825	$86.18	$86.20	$86.20
7 purchase totals =	$945.33		$1,035.7279	$1,035.73	$1,035.70	$1,035.70