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	$220.55	8.625%	$239.5724	$239.57	$239.55	$239.60
Purchase #2	$20.96	13.499%	$23.7894	$23.79	$23.80	$23.80
Purchase #3	$116.69	8.863%	$127.0322	$127.03	$127.05	$127.00
Purchase #4	$83.29	4.549%	$87.0789	$87.08	$87.10	$87.10
Purchase #5	$250.83	7.699%	$270.1414	$270.14	$270.15	$270.10
Purchase #6	$86.27	4.494%	$90.147	$90.15	$90.15	$90.10
Purchase #7	$154.83	6.506%	$164.9032	$164.90	$164.90	$164.90
7 purchase totals =	$933.42		$1,002.6645	$1,002.66	$1,002.70	$1,002.60