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	$145.61	7.122%	$155.9803	$155.98	$156.00	$156.00
Purchase #2	$60.88	13.868%	$69.3228	$69.32	$69.30	$69.30
Purchase #3	$143.48	8.355%	$155.4678	$155.47	$155.45	$155.50
Purchase #4	$190.36	3.165%	$196.3849	$196.38	$196.40	$196.40
Purchase #5	$177.99	11.483%	$198.4286	$198.43	$198.45	$198.40
Purchase #6	$92.60	6.788%	$98.8857	$98.89	$98.90	$98.90
Purchase #7	$50.86	13.252%	$57.6	$57.60	$57.60	$57.60
7 purchase totals =	$861.78		$932.0701	$932.07	$932.10	$932.10