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	$66.43	4.460%	$69.3928	$69.39	$69.40	$69.40
Purchase #2	$202.78	10.389%	$223.8468	$223.85	$223.85	$223.80
Purchase #3	$113.96	8.602%	$123.7628	$123.76	$123.75	$123.80
Purchase #4	$38.94	3.323%	$40.234	$40.23	$40.25	$40.20
Purchase #5	$19.48	3.170%	$20.0975	$20.10	$20.10	$20.10
Purchase #6	$46.77	8.127%	$50.571	$50.57	$50.55	$50.60
Purchase #7	$17.44	11.587%	$19.4608	$19.46	$19.45	$19.50
7 purchase totals =	$505.80		$547.3657	$547.36	$547.35	$547.40