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	$62.37	8.586%	$67.7251	$67.73	$67.75	$67.70
Purchase #2	$10.47	10.294%	$11.5478	$11.55	$11.55	$11.50
Purchase #3	$103.88	8.816%	$113.0381	$113.04	$113.05	$113.00
Purchase #4	$71.93	3.193%	$74.2267	$74.23	$74.25	$74.20
Purchase #5	$148.66	12.693%	$167.5294	$167.53	$167.55	$167.50
Purchase #6	$97.40	8.643%	$105.8183	$105.82	$105.80	$105.80
Purchase #7	$99.25	6.168%	$105.3717	$105.37	$105.35	$105.40
7 purchase totals =	$593.96		$645.2571	$645.27	$645.30	$645.10