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	$83.88	13.730%	$95.3967	$95.40	$95.40	$95.40
Purchase #2	$79.65	8.102%	$86.1032	$86.10	$86.10	$86.10
Purchase #3	$163.34	4.825%	$171.2212	$171.22	$171.20	$171.20
Purchase #4	$47.71	7.705%	$51.3861	$51.39	$51.40	$51.40
Purchase #5	$32.48	8.271%	$35.1664	$35.17	$35.15	$35.20
Purchase #6	$113.86	11.775%	$127.267	$127.27	$127.25	$127.30
Purchase #7	$47.60	7.714%	$51.2719	$51.27	$51.25	$51.30
7 purchase totals =	$568.52		$617.8125	$617.82	$617.75	$617.90