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	$137.93	3.151%	$142.2762	$142.28	$142.30	$142.30
Purchase #2	$228.87	7.157%	$245.2502	$245.25	$245.25	$245.30
Purchase #3	$97.26	5.517%	$102.6258	$102.63	$102.65	$102.60
Purchase #4	$173.74	13.175%	$196.6302	$196.63	$196.65	$196.60
Purchase #5	$103.26	8.362%	$111.8946	$111.89	$111.90	$111.90
Purchase #6	$102.47	7.770%	$110.4319	$110.43	$110.45	$110.40
Purchase #7	$153.79	4.771%	$161.1273	$161.13	$161.15	$161.10
7 purchase totals =	$997.32		$1,070.2362	$1,070.24	$1,070.35	$1,070.20