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	$67.51	4.686%	$70.6735	$70.67	$70.65	$70.70
Purchase #2	$186.50	7.614%	$200.7001	$200.70	$200.70	$200.70
Purchase #3	$112.72	6.436%	$119.9747	$119.97	$119.95	$120.00
Purchase #4	$21.95	3.509%	$22.7202	$22.72	$22.70	$22.70
Purchase #5	$82.31	9.200%	$89.8825	$89.88	$89.90	$89.90
Purchase #6	$199.37	5.586%	$210.5068	$210.51	$210.50	$210.50
Purchase #7	$78.32	9.689%	$85.9084	$85.91	$85.90	$85.90
7 purchase totals =	$748.68		$800.3662	$800.36	$800.30	$800.40