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	$93.68	6.238%	$99.5238	$99.52	$99.50	$99.50
Purchase #2	$31.30	13.319%	$35.4688	$35.47	$35.45	$35.50
Purchase #3	$217.85	12.874%	$245.896	$245.90	$245.90	$245.90
Purchase #4	$59.36	13.256%	$67.2288	$67.23	$67.25	$67.20
Purchase #5	$133.92	5.297%	$141.0137	$141.01	$141.00	$141.00
Purchase #6	$246.46	10.361%	$271.9957	$272.00	$272.00	$272.00
Purchase #7	$140.32	7.231%	$150.4665	$150.47	$150.45	$150.50
7 purchase totals =	$922.89		$1,011.5933	$1,011.60	$1,011.55	$1,011.60