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	$232.37	11.790%	$259.7664	$259.77	$259.75	$259.80
Purchase #2	$184.77	12.153%	$207.2251	$207.23	$207.25	$207.20
Purchase #3	$41.27	10.707%	$45.6888	$45.69	$45.70	$45.70
Purchase #4	$143.46	10.553%	$158.5993	$158.60	$158.60	$158.60
Purchase #5	$171.92	3.804%	$178.4598	$178.46	$178.45	$178.50
Purchase #6	$163.67	13.576%	$185.8898	$185.89	$185.90	$185.90
Purchase #7	$175.25	13.746%	$199.3399	$199.34	$199.35	$199.30
7 purchase totals =	$1,112.71		$1,234.9691	$1,234.98	$1,235.00	$1,235.00