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	$241.76	3.174%	$249.4335	$249.43	$249.45	$249.40
Purchase #2	$246.38	8.139%	$266.4329	$266.43	$266.45	$266.40
Purchase #3	$162.29	11.614%	$181.1384	$181.14	$181.15	$181.10
Purchase #4	$146.50	9.153%	$159.9091	$159.91	$159.90	$159.90
Purchase #5	$102.37	9.120%	$111.7061	$111.71	$111.70	$111.70
Purchase #6	$127.83	6.556%	$136.2105	$136.21	$136.20	$136.20
Purchase #7	$53.85	9.820%	$59.1381	$59.14	$59.15	$59.10
7 purchase totals =	$1,080.98		$1,163.9686	$1,163.97	$1,164.00	$1,163.80