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	$131.48	9.153%	$143.5144	$143.51	$143.50	$143.50
Purchase #2	$43.25	7.503%	$46.495	$46.50	$46.50	$46.50
Purchase #3	$171.43	8.364%	$185.7684	$185.77	$185.75	$185.80
Purchase #4	$163.57	9.849%	$179.68	$179.68	$179.70	$179.70
Purchase #5	$167.89	6.799%	$179.3048	$179.30	$179.30	$179.30
Purchase #6	$143.42	8.873%	$156.1457	$156.15	$156.15	$156.10
Purchase #7	$145.71	8.310%	$157.8185	$157.82	$157.80	$157.80
7 purchase totals =	$966.75		$1,048.7268	$1,048.73	$1,048.70	$1,048.70