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	$128.88	13.755%	$146.6074	$146.61	$146.60	$146.60
Purchase #2	$217.39	4.627%	$227.4486	$227.45	$227.45	$227.40
Purchase #3	$155.42	8.260%	$168.2577	$168.26	$168.25	$168.30
Purchase #4	$40.45	6.402%	$43.0396	$43.04	$43.05	$43.00
Purchase #5	$217.55	10.740%	$240.9149	$240.91	$240.90	$240.90
Purchase #6	$227.65	4.731%	$238.4201	$238.42	$238.40	$238.40
Purchase #7	$162.49	12.522%	$182.837	$182.84	$182.85	$182.80
7 purchase totals =	$1,149.83		$1,247.5253	$1,247.53	$1,247.50	$1,247.40