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	$103.34	8.738%	$112.3698	$112.37	$112.35	$112.40
Purchase #2	$64.32	9.235%	$70.26	$70.26	$70.25	$70.30
Purchase #3	$213.30	13.843%	$242.8271	$242.83	$242.85	$242.80
Purchase #4	$43.94	3.369%	$45.4203	$45.42	$45.40	$45.40
Purchase #5	$25.50	8.337%	$27.6259	$27.63	$27.65	$27.60
Purchase #6	$36.53	9.146%	$39.871	$39.87	$39.85	$39.90
Purchase #7	$162.57	5.723%	$171.8739	$171.87	$171.85	$171.90
7 purchase totals =	$649.50		$710.2480	$710.25	$710.20	$710.30