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	$212.55	5.702%	$224.6696	$224.67	$224.65	$224.70
Purchase #2	$82.66	3.340%	$85.4208	$85.42	$85.40	$85.40
Purchase #3	$113.55	12.702%	$127.9731	$127.97	$127.95	$128.00
Purchase #4	$78.78	4.273%	$82.1463	$82.15	$82.15	$82.10
Purchase #5	$202.75	7.589%	$218.1367	$218.14	$218.15	$218.10
Purchase #6	$62.44	3.520%	$64.6379	$64.64	$64.65	$64.60
Purchase #7	$232.67	10.254%	$256.528	$256.53	$256.55	$256.50
7 purchase totals =	$985.40		$1,059.5124	$1,059.52	$1,059.50	$1,059.40