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	$232.67	6.421%	$247.6097	$247.61	$247.60	$247.60
Purchase #2	$160.45	7.688%	$172.7854	$172.79	$172.80	$172.80
Purchase #3	$43.90	9.195%	$47.9366	$47.94	$47.95	$47.90
Purchase #4	$101.83	10.295%	$112.3134	$112.31	$112.30	$112.30
Purchase #5	$113.52	9.720%	$124.5541	$124.55	$124.55	$124.60
Purchase #6	$169.96	11.531%	$189.5581	$189.56	$189.55	$189.60
Purchase #7	$105.57	11.638%	$117.8562	$117.86	$117.85	$117.90
7 purchase totals =	$927.90		$1,012.6135	$1,012.62	$1,012.60	$1,012.70