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	$162.89	6.432%	$173.3671	$173.37	$173.35	$173.40
Purchase #2	$170.65	11.291%	$189.9181	$189.92	$189.90	$189.90
Purchase #3	$100.31	9.629%	$109.9688	$109.97	$109.95	$110.00
Purchase #4	$165.60	10.439%	$182.887	$182.89	$182.90	$182.90
Purchase #5	$171.65	12.257%	$192.6891	$192.69	$192.70	$192.70
Purchase #6	$36.31	11.603%	$40.523	$40.52	$40.50	$40.50
Purchase #7	$80.53	8.172%	$87.1109	$87.11	$87.10	$87.10
7 purchase totals =	$887.94		$976.4640	$976.47	$976.40	$976.50