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	$177.66	8.259%	$192.3329	$192.33	$192.35	$192.30
Purchase #2	$185.36	6.200%	$196.8523	$196.85	$196.85	$196.90
Purchase #3	$120.33	9.532%	$131.7999	$131.80	$131.80	$131.80
Purchase #4	$202.37	8.363%	$219.2942	$219.29	$219.30	$219.30
Purchase #5	$240.53	12.548%	$270.7117	$270.71	$270.70	$270.70
Purchase #6	$126.81	4.386%	$132.3719	$132.37	$132.35	$132.40
Purchase #7	$90.32	11.346%	$100.5677	$100.57	$100.55	$100.60
7 purchase totals =	$1,143.38		$1,243.9306	$1,243.92	$1,243.90	$1,244.00