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	$237.34	7.394%	$254.8889	$254.89	$254.90	$254.90
Purchase #2	$95.69	5.465%	$100.9195	$100.92	$100.90	$100.90
Purchase #3	$210.73	7.573%	$226.6886	$226.69	$226.70	$226.70
Purchase #4	$187.25	5.555%	$197.6517	$197.65	$197.65	$197.70
Purchase #5	$52.99	3.585%	$54.8897	$54.89	$54.90	$54.90
Purchase #6	$113.76	12.365%	$127.8264	$127.83	$127.85	$127.80
Purchase #7	$161.88	11.819%	$181.0126	$181.01	$181.00	$181.00
7 purchase totals =	$1,059.64		$1,143.8774	$1,143.88	$1,143.90	$1,143.90