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	$76.98	7.650%	$82.869	$82.87	$82.85	$82.90
Purchase #2	$122.49	13.591%	$139.1376	$139.14	$139.15	$139.10
Purchase #3	$49.58	12.296%	$55.6764	$55.68	$55.70	$55.70
Purchase #4	$44.95	4.582%	$47.0096	$47.01	$47.00	$47.00
Purchase #5	$168.35	6.599%	$179.4594	$179.46	$179.45	$179.50
Purchase #6	$82.46	12.715%	$92.9448	$92.94	$92.95	$92.90
Purchase #7	$136.99	9.667%	$150.2328	$150.23	$150.25	$150.20
7 purchase totals =	$681.80		$747.3296	$747.33	$747.35	$747.30