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	$163.95	13.469%	$186.0324	$186.03	$186.05	$186.00
Purchase #2	$233.97	13.379%	$265.2728	$265.27	$265.25	$265.30
Purchase #3	$39.46	11.200%	$43.8795	$43.88	$43.90	$43.90
Purchase #4	$231.32	10.493%	$255.5924	$255.59	$255.60	$255.60
Purchase #5	$55.61	7.528%	$59.7963	$59.80	$59.80	$59.80
Purchase #6	$120.75	12.755%	$136.1517	$136.15	$136.15	$136.20
Purchase #7	$180.63	6.791%	$192.8966	$192.90	$192.90	$192.90
7 purchase totals =	$1,025.69		$1,139.6217	$1,139.62	$1,139.65	$1,139.70