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	$239.91	9.586%	$262.9078	$262.91	$262.90	$262.90
Purchase #2	$104.86	4.860%	$109.9562	$109.96	$109.95	$110.00
Purchase #3	$246.59	3.733%	$255.7952	$255.80	$255.80	$255.80
Purchase #4	$126.40	12.562%	$142.2784	$142.28	$142.30	$142.30
Purchase #5	$228.86	4.826%	$239.9048	$239.90	$239.90	$239.90
Purchase #6	$87.88	4.838%	$92.1316	$92.13	$92.15	$92.10
Purchase #7	$248.32	7.468%	$266.8645	$266.86	$266.85	$266.90
7 purchase totals =	$1,282.82		$1,369.8385	$1,369.84	$1,369.85	$1,369.90