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	$184.58	8.709%	$200.6551	$200.66	$200.65	$200.70
Purchase #2	$135.83	3.695%	$140.8489	$140.85	$140.85	$140.80
Purchase #3	$219.93	4.826%	$230.5438	$230.54	$230.55	$230.50
Purchase #4	$89.27	5.515%	$94.1932	$94.19	$94.20	$94.20
Purchase #5	$88.78	12.408%	$99.7958	$99.80	$99.80	$99.80
Purchase #6	$25.39	10.589%	$28.0785	$28.08	$28.10	$28.10
Purchase #7	$137.66	9.632%	$150.9194	$150.92	$150.90	$150.90
7 purchase totals =	$881.44		$945.0347	$945.04	$945.05	$945.00