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	$132.74	7.558%	$142.7725	$142.77	$142.75	$142.80
Purchase #2	$83.58	6.343%	$88.8815	$88.88	$88.90	$88.90
Purchase #3	$36.67	13.116%	$41.4796	$41.48	$41.50	$41.50
Purchase #4	$248.65	3.493%	$257.3353	$257.34	$257.35	$257.30
Purchase #5	$177.79	6.102%	$188.6387	$188.64	$188.65	$188.60
Purchase #6	$79.62	12.444%	$89.5279	$89.53	$89.55	$89.50
Purchase #7	$192.39	12.509%	$216.4561	$216.46	$216.45	$216.50
7 purchase totals =	$951.44		$1,025.0916	$1,025.10	$1,025.15	$1,025.10