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	$144.62	12.603%	$162.8465	$162.85	$162.85	$162.80
Purchase #2	$32.59	6.827%	$34.8149	$34.81	$34.80	$34.80
Purchase #3	$75.31	9.312%	$82.3229	$82.32	$82.30	$82.30
Purchase #4	$95.88	11.509%	$106.9148	$106.91	$106.90	$106.90
Purchase #5	$171.89	10.320%	$189.629	$189.63	$189.65	$189.60
Purchase #6	$175.94	9.407%	$192.4907	$192.49	$192.50	$192.50
Purchase #7	$164.74	12.730%	$185.7114	$185.71	$185.70	$185.70
7 purchase totals =	$860.97		$954.7302	$954.72	$954.70	$954.60