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	$38.49	8.172%	$41.6354	$41.64	$41.65	$41.60
Purchase #2	$63.74	5.308%	$67.1233	$67.12	$67.10	$67.10
Purchase #3	$35.38	6.804%	$37.7873	$37.79	$37.80	$37.80
Purchase #4	$9.95	9.301%	$10.8754	$10.88	$10.90	$10.90
Purchase #5	$133.94	4.577%	$140.0704	$140.07	$140.05	$140.10
Purchase #6	$134.48	11.734%	$150.2599	$150.26	$150.25	$150.30
Purchase #7	$162.27	4.600%	$169.7344	$169.73	$169.75	$169.70
7 purchase totals =	$578.25		$617.4861	$617.49	$617.50	$617.50