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	$150.73	3.678%	$156.2738	$156.27	$156.25	$156.30
Purchase #2	$185.47	5.856%	$196.3311	$196.33	$196.35	$196.30
Purchase #3	$150.91	8.569%	$163.8415	$163.84	$163.85	$163.80
Purchase #4	$95.83	4.703%	$100.3369	$100.34	$100.35	$100.30
Purchase #5	$224.32	4.611%	$234.6634	$234.66	$234.65	$234.70
Purchase #6	$83.95	8.192%	$90.8272	$90.83	$90.85	$90.80
Purchase #7	$86.53	5.175%	$91.0079	$91.01	$91.00	$91.00
7 purchase totals =	$977.74		$1,033.2818	$1,033.28	$1,033.30	$1,033.20