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	$73.37	11.731%	$81.977	$81.98	$82.00	$82.00
Purchase #2	$248.82	9.337%	$272.0523	$272.05	$272.05	$272.10
Purchase #3	$98.78	5.591%	$104.3028	$104.30	$104.30	$104.30
Purchase #4	$80.85	12.280%	$90.7784	$90.78	$90.80	$90.80
Purchase #5	$122.77	13.405%	$139.2273	$139.23	$139.25	$139.20
Purchase #6	$196.75	3.245%	$203.1345	$203.13	$203.15	$203.10
Purchase #7	$131.27	9.674%	$143.9691	$143.97	$143.95	$144.00
7 purchase totals =	$952.61		$1,035.4414	$1,035.44	$1,035.50	$1,035.50