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	$139.44	10.800%	$154.4995	$154.50	$154.50	$154.50
Purchase #2	$83.50	3.392%	$86.3323	$86.33	$86.35	$86.30
Purchase #3	$28.71	11.389%	$31.9798	$31.98	$32.00	$32.00
Purchase #4	$153.58	5.639%	$162.2404	$162.24	$162.25	$162.20
Purchase #5	$89.42	10.554%	$98.8574	$98.86	$98.85	$98.90
Purchase #6	$171.82	13.643%	$195.2614	$195.26	$195.25	$195.30
Purchase #7	$68.83	4.582%	$71.9838	$71.98	$72.00	$72.00
7 purchase totals =	$735.30		$801.1546	$801.15	$801.20	$801.20