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	$240.47	10.347%	$265.3514	$265.35	$265.35	$265.40
Purchase #2	$85.53	9.556%	$93.7032	$93.70	$93.70	$93.70
Purchase #3	$82.52	8.135%	$89.233	$89.23	$89.25	$89.20
Purchase #4	$37.62	13.620%	$42.7438	$42.74	$42.75	$42.70
Purchase #5	$238.47	7.127%	$255.4658	$255.47	$255.45	$255.50
Purchase #6	$101.78	12.444%	$114.4455	$114.45	$114.45	$114.40
Purchase #7	$193.92	9.752%	$212.8311	$212.83	$212.85	$212.80
7 purchase totals =	$980.31		$1,073.7738	$1,073.77	$1,073.80	$1,073.70