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	$212.90	11.546%	$237.4814	$237.48	$237.50	$237.50
Purchase #2	$139.27	9.485%	$152.4798	$152.48	$152.50	$152.50
Purchase #3	$151.51	7.755%	$163.2596	$163.26	$163.25	$163.30
Purchase #4	$61.89	8.741%	$67.2998	$67.30	$67.30	$67.30
Purchase #5	$64.80	6.755%	$69.1772	$69.18	$69.20	$69.20
Purchase #6	$98.86	10.813%	$109.5497	$109.55	$109.55	$109.50
Purchase #7	$144.37	12.425%	$162.308	$162.31	$162.30	$162.30
7 purchase totals =	$873.60		$961.5555	$961.56	$961.60	$961.60