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	$195.41	13.800%	$222.3766	$222.38	$222.40	$222.40
Purchase #2	$233.39	10.702%	$258.3674	$258.37	$258.35	$258.40
Purchase #3	$228.86	5.134%	$240.6097	$240.61	$240.60	$240.60
Purchase #4	$144.46	12.709%	$162.8194	$162.82	$162.80	$162.80
Purchase #5	$8.54	4.821%	$8.9517	$8.95	$8.95	$9.00
Purchase #6	$51.32	5.360%	$54.0708	$54.07	$54.05	$54.10
Purchase #7	$198.69	11.521%	$221.5811	$221.58	$221.60	$221.60
7 purchase totals =	$1,060.67		$1,168.7767	$1,168.78	$1,168.75	$1,168.90