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	$5.97	4.741%	$6.253	$6.25	$6.25	$6.30
Purchase #2	$178.46	10.170%	$196.6094	$196.61	$196.60	$196.60
Purchase #3	$139.46	12.534%	$156.9399	$156.94	$156.95	$156.90
Purchase #4	$209.92	5.861%	$222.2234	$222.22	$222.20	$222.20
Purchase #5	$55.26	11.334%	$61.5232	$61.52	$61.50	$61.50
Purchase #6	$155.39	4.388%	$162.2085	$162.21	$162.20	$162.20
Purchase #7	$86.63	5.418%	$91.3236	$91.32	$91.30	$91.30
7 purchase totals =	$831.09		$897.0810	$897.07	$897.00	$897.00