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	$118.69	5.541%	$125.2666	$125.27	$125.25	$125.30
Purchase #2	$73.61	7.141%	$78.8665	$78.87	$78.85	$78.90
Purchase #3	$34.86	5.661%	$36.8334	$36.83	$36.85	$36.80
Purchase #4	$172.89	3.239%	$178.4899	$178.49	$178.50	$178.50
Purchase #5	$72.82	10.769%	$80.662	$80.66	$80.65	$80.70
Purchase #6	$190.54	8.354%	$206.4577	$206.46	$206.45	$206.50
Purchase #7	$142.89	12.483%	$160.727	$160.73	$160.75	$160.70
7 purchase totals =	$806.30		$867.3031	$867.31	$867.30	$867.40