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	$85.47	3.352%	$88.335	$88.34	$88.35	$88.30
Purchase #2	$141.67	10.480%	$156.517	$156.52	$156.50	$156.50
Purchase #3	$65.54	6.441%	$69.7614	$69.76	$69.75	$69.80
Purchase #4	$201.34	11.389%	$224.2706	$224.27	$224.25	$224.30
Purchase #5	$24.54	3.423%	$25.38	$25.38	$25.40	$25.40
Purchase #6	$212.87	13.824%	$242.2971	$242.30	$242.30	$242.30
Purchase #7	$93.82	11.795%	$104.8861	$104.89	$104.90	$104.90
7 purchase totals =	$825.25		$911.4472	$911.46	$911.45	$911.50