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	$100.92	5.579%	$106.5503	$106.55	$106.55	$106.60
Purchase #2	$137.99	13.294%	$156.3344	$156.33	$156.35	$156.30
Purchase #3	$38.85	11.793%	$43.4316	$43.43	$43.45	$43.40
Purchase #4	$175.77	12.759%	$198.1965	$198.20	$198.20	$198.20
Purchase #5	$200.71	12.356%	$225.5097	$225.51	$225.50	$225.50
Purchase #6	$146.76	8.193%	$158.784	$158.78	$158.80	$158.80
Purchase #7	$154.54	4.538%	$161.553	$161.55	$161.55	$161.60
7 purchase totals =	$955.54		$1,050.3595	$1,050.35	$1,050.40	$1,050.40