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	$141.47	9.325%	$154.6621	$154.66	$154.65	$154.70
Purchase #2	$225.88	10.435%	$249.4506	$249.45	$249.45	$249.50
Purchase #3	$141.85	9.854%	$155.8279	$155.83	$155.85	$155.80
Purchase #4	$178.73	5.695%	$188.9087	$188.91	$188.90	$188.90
Purchase #5	$139.61	8.796%	$151.8901	$151.89	$151.90	$151.90
Purchase #6	$92.57	11.811%	$103.5034	$103.50	$103.50	$103.50
Purchase #7	$167.50	9.811%	$183.9334	$183.93	$183.95	$183.90
7 purchase totals =	$1,087.61		$1,188.1762	$1,188.17	$1,188.20	$1,188.20