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	$147.77	8.639%	$160.5359	$160.54	$160.55	$160.50
Purchase #2	$144.87	3.792%	$150.3635	$150.36	$150.35	$150.40
Purchase #3	$219.47	7.108%	$235.0699	$235.07	$235.05	$235.10
Purchase #4	$118.94	10.342%	$131.2408	$131.24	$131.25	$131.20
Purchase #5	$152.98	12.455%	$172.0337	$172.03	$172.05	$172.00
Purchase #6	$125.80	7.266%	$134.9406	$134.94	$134.95	$134.90
Purchase #7	$234.47	9.309%	$256.2968	$256.30	$256.30	$256.30
7 purchase totals =	$1,144.30		$1,240.4812	$1,240.48	$1,240.50	$1,240.40