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	$107.91	8.754%	$117.3564	$117.36	$117.35	$117.40
Purchase #2	$72.34	5.388%	$76.2377	$76.24	$76.25	$76.20
Purchase #3	$92.49	6.804%	$98.783	$98.78	$98.80	$98.80
Purchase #4	$176.65	3.306%	$182.49	$182.49	$182.50	$182.50
Purchase #5	$208.32	6.831%	$222.5503	$222.55	$222.55	$222.60
Purchase #6	$210.33	3.724%	$218.1627	$218.16	$218.15	$218.20
Purchase #7	$119.55	10.342%	$131.9139	$131.91	$131.90	$131.90
7 purchase totals =	$987.59		$1,047.4940	$1,047.49	$1,047.50	$1,047.60