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	$191.31	11.272%	$212.8745	$212.87	$212.85	$212.90
Purchase #2	$112.71	3.659%	$116.8341	$116.83	$116.85	$116.80
Purchase #3	$29.82	9.218%	$32.5688	$32.57	$32.55	$32.60
Purchase #4	$72.93	6.845%	$77.9221	$77.92	$77.90	$77.90
Purchase #5	$150.71	12.607%	$169.71	$169.71	$169.70	$169.70
Purchase #6	$221.25	9.827%	$242.9922	$242.99	$243.00	$243.00
Purchase #7	$183.53	13.578%	$208.4497	$208.45	$208.45	$208.40
7 purchase totals =	$962.26		$1,061.3514	$1,061.34	$1,061.30	$1,061.30