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	$54.42	8.864%	$59.2438	$59.24	$59.25	$59.20
Purchase #2	$15.89	11.796%	$17.7644	$17.76	$17.75	$17.80
Purchase #3	$199.31	6.799%	$212.8611	$212.86	$212.85	$212.90
Purchase #4	$11.94	12.865%	$13.4761	$13.48	$13.50	$13.50
Purchase #5	$109.28	9.420%	$119.5742	$119.57	$119.55	$119.60
Purchase #6	$212.73	5.172%	$223.7324	$223.73	$223.75	$223.70
Purchase #7	$81.59	3.265%	$84.2539	$84.25	$84.25	$84.30
7 purchase totals =	$685.16		$730.9059	$730.89	$730.90	$731.00