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	$146.81	10.489%	$162.2089	$162.21	$162.20	$162.20
Purchase #2	$116.43	13.119%	$131.7045	$131.70	$131.70	$131.70
Purchase #3	$213.82	5.380%	$225.3235	$225.32	$225.30	$225.30
Purchase #4	$158.25	8.278%	$171.3499	$171.35	$171.35	$171.30
Purchase #5	$112.29	10.404%	$123.9727	$123.97	$123.95	$124.00
Purchase #6	$86.29	5.123%	$90.7106	$90.71	$90.70	$90.70
Purchase #7	$121.42	13.506%	$137.819	$137.82	$137.80	$137.80
7 purchase totals =	$955.31		$1,043.0891	$1,043.08	$1,043.00	$1,043.00