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	$76.90	7.403%	$82.5929	$82.59	$82.60	$82.60
Purchase #2	$104.91	4.183%	$109.2984	$109.30	$109.30	$109.30
Purchase #3	$193.37	3.154%	$199.4689	$199.47	$199.45	$199.50
Purchase #4	$215.29	8.609%	$233.8243	$233.82	$233.80	$233.80
Purchase #5	$249.96	6.421%	$266.0099	$266.01	$266.00	$266.00
Purchase #6	$76.45	7.426%	$82.1272	$82.13	$82.15	$82.10
Purchase #7	$223.99	13.374%	$253.9464	$253.95	$253.95	$253.90
7 purchase totals =	$1,140.87		$1,227.2680	$1,227.27	$1,227.25	$1,227.20