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	$202.45	5.158%	$212.8924	$212.89	$212.90	$212.90
Purchase #2	$199.85	13.726%	$227.2814	$227.28	$227.30	$227.30
Purchase #3	$106.49	3.191%	$109.8881	$109.89	$109.90	$109.90
Purchase #4	$98.57	12.874%	$111.2599	$111.26	$111.25	$111.30
Purchase #5	$27.35	8.673%	$29.7221	$29.72	$29.70	$29.70
Purchase #6	$131.83	3.304%	$136.1857	$136.19	$136.20	$136.20
Purchase #7	$140.43	5.662%	$148.3811	$148.38	$148.40	$148.40
7 purchase totals =	$906.97		$975.6107	$975.61	$975.65	$975.70