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	$192.67	9.240%	$210.4727	$210.47	$210.45	$210.50
Purchase #2	$206.89	4.832%	$216.8869	$216.89	$216.90	$216.90
Purchase #3	$234.40	3.630%	$242.9087	$242.91	$242.90	$242.90
Purchase #4	$20.87	11.741%	$23.3203	$23.32	$23.30	$23.30
Purchase #5	$12.27	6.734%	$13.0963	$13.10	$13.10	$13.10
Purchase #6	$208.26	5.776%	$220.2891	$220.29	$220.30	$220.30
Purchase #7	$86.34	4.664%	$90.3669	$90.37	$90.35	$90.40
7 purchase totals =	$961.70		$1,017.3409	$1,017.35	$1,017.30	$1,017.40