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	$111.83	10.312%	$123.3619	$123.36	$123.35	$123.40
Purchase #2	$249.96	4.864%	$262.1181	$262.12	$262.10	$262.10
Purchase #3	$87.95	4.791%	$92.1637	$92.16	$92.15	$92.20
Purchase #4	$154.48	6.239%	$164.118	$164.12	$164.10	$164.10
Purchase #5	$197.86	6.312%	$210.3489	$210.35	$210.35	$210.30
Purchase #6	$9.76	5.496%	$10.2964	$10.30	$10.30	$10.30
Purchase #7	$215.35	4.704%	$225.4801	$225.48	$225.50	$225.50
7 purchase totals =	$1,027.19		$1,087.8871	$1,087.89	$1,087.85	$1,087.90