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	$211.69	4.620%	$221.4701	$221.47	$221.45	$221.50
Purchase #2	$79.61	5.178%	$83.7322	$83.73	$83.75	$83.70
Purchase #3	$224.50	6.421%	$238.9151	$238.92	$238.90	$238.90
Purchase #4	$125.74	3.746%	$130.4502	$130.45	$130.45	$130.50
Purchase #5	$59.50	6.666%	$63.4663	$63.47	$63.45	$63.50
Purchase #6	$26.45	4.352%	$27.6011	$27.60	$27.60	$27.60
Purchase #7	$111.63	4.820%	$117.0106	$117.01	$117.00	$117.00
7 purchase totals =	$839.12		$882.6456	$882.65	$882.60	$882.70