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	$109.87	9.774%	$120.6087	$120.61	$120.60	$120.60
Purchase #2	$188.25	9.807%	$206.7117	$206.71	$206.70	$206.70
Purchase #3	$167.86	13.391%	$190.3381	$190.34	$190.35	$190.30
Purchase #4	$121.52	10.865%	$134.7231	$134.72	$134.70	$134.70
Purchase #5	$241.33	9.783%	$264.9393	$264.94	$264.95	$264.90
Purchase #6	$234.71	11.182%	$260.9553	$260.96	$260.95	$261.00
Purchase #7	$210.90	5.685%	$222.8897	$222.89	$222.90	$222.90
7 purchase totals =	$1,274.44		$1,401.1659	$1,401.17	$1,401.15	$1,401.10