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	$213.26	12.754%	$240.4592	$240.46	$240.45	$240.50
Purchase #2	$86.54	3.162%	$89.2764	$89.28	$89.30	$89.30
Purchase #3	$168.29	10.434%	$185.8494	$185.85	$185.85	$185.80
Purchase #4	$210.87	3.263%	$217.7507	$217.75	$217.75	$217.80
Purchase #5	$117.58	8.761%	$127.8812	$127.88	$127.90	$127.90
Purchase #6	$47.80	8.620%	$51.9204	$51.92	$51.90	$51.90
Purchase #7	$102.79	6.160%	$109.1219	$109.12	$109.10	$109.10
7 purchase totals =	$947.13		$1,022.2592	$1,022.26	$1,022.25	$1,022.30