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	$206.94	6.569%	$220.5339	$220.53	$220.55	$220.50
Purchase #2	$38.38	6.545%	$40.892	$40.89	$40.90	$40.90
Purchase #3	$31.46	12.352%	$35.3459	$35.35	$35.35	$35.30
Purchase #4	$22.41	11.855%	$25.0667	$25.07	$25.05	$25.10
Purchase #5	$229.37	9.205%	$250.4835	$250.48	$250.50	$250.50
Purchase #6	$77.59	7.610%	$83.4946	$83.49	$83.50	$83.50
Purchase #7	$148.46	12.530%	$167.062	$167.06	$167.05	$167.10
7 purchase totals =	$754.61		$822.8786	$822.87	$822.90	$822.90