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	$60.66	10.439%	$66.9923	$66.99	$67.00	$67.00
Purchase #2	$156.35	12.764%	$176.3065	$176.31	$176.30	$176.30
Purchase #3	$25.60	5.615%	$27.0374	$27.04	$27.05	$27.00
Purchase #4	$36.83	4.824%	$38.6067	$38.61	$38.60	$38.60
Purchase #5	$59.64	7.751%	$64.2627	$64.26	$64.25	$64.30
Purchase #6	$189.75	3.655%	$196.6854	$196.69	$196.70	$196.70
Purchase #7	$202.71	9.776%	$222.5269	$222.53	$222.55	$222.50
7 purchase totals =	$731.54		$792.4179	$792.43	$792.45	$792.40