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	$197.42	13.406%	$223.8861	$223.89	$223.90	$223.90
Purchase #2	$203.66	7.857%	$219.6616	$219.66	$219.65	$219.70
Purchase #3	$109.76	12.870%	$123.8861	$123.89	$123.90	$123.90
Purchase #4	$157.46	6.232%	$167.2729	$167.27	$167.25	$167.30
Purchase #5	$59.50	5.311%	$62.66	$62.66	$62.65	$62.70
Purchase #6	$104.96	6.319%	$111.5924	$111.59	$111.60	$111.60
Purchase #7	$213.69	6.577%	$227.7444	$227.74	$227.75	$227.70
7 purchase totals =	$1,046.45		$1,136.7035	$1,136.70	$1,136.70	$1,136.80