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	$43.46	4.667%	$45.4883	$45.49	$45.50	$45.50
Purchase #2	$192.26	8.822%	$209.2212	$209.22	$209.20	$209.20
Purchase #3	$29.47	11.378%	$32.8231	$32.82	$32.80	$32.80
Purchase #4	$79.84	12.224%	$89.5996	$89.60	$89.60	$89.60
Purchase #5	$226.41	4.652%	$236.9426	$236.94	$236.95	$236.90
Purchase #6	$187.66	12.371%	$210.8754	$210.88	$210.90	$210.90
Purchase #7	$219.53	9.407%	$240.1812	$240.18	$240.20	$240.20
7 purchase totals =	$978.63		$1,065.1314	$1,065.13	$1,065.15	$1,065.10