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	$147.78	8.757%	$160.7211	$160.72	$160.70	$160.70
Purchase #2	$109.50	8.764%	$119.0966	$119.10	$119.10	$119.10
Purchase #3	$76.37	7.873%	$82.3826	$82.38	$82.40	$82.40
Purchase #4	$226.56	3.484%	$234.4534	$234.45	$234.45	$234.50
Purchase #5	$141.82	13.116%	$160.4211	$160.42	$160.40	$160.40
Purchase #6	$155.83	5.173%	$163.8911	$163.89	$163.90	$163.90
Purchase #7	$76.46	13.692%	$86.9289	$86.93	$86.95	$86.90
7 purchase totals =	$934.32		$1,007.8948	$1,007.89	$1,007.90	$1,007.90