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	$111.25	6.865%	$118.8873	$118.89	$118.90	$118.90
Purchase #2	$157.95	5.755%	$167.04	$167.04	$167.05	$167.00
Purchase #3	$220.92	11.108%	$245.4598	$245.46	$245.45	$245.50
Purchase #4	$51.48	9.495%	$56.368	$56.37	$56.35	$56.40
Purchase #5	$23.59	8.582%	$25.6145	$25.61	$25.60	$25.60
Purchase #6	$67.66	3.187%	$69.8163	$69.82	$69.80	$69.80
Purchase #7	$64.78	11.782%	$72.4124	$72.41	$72.40	$72.40
7 purchase totals =	$697.63		$755.5983	$755.60	$755.55	$755.60